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Day 3. Teach Epidemiology. Professional Development Workshop. Centers for Disease Control and Prevention Global Health Odyssey Museum Tom Harkin Global Communications Center June 6-10, 2011. Teach Epidemiology. Teach Epidemiology.

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slide1

Day

3

Teach Epidemiology

Professional Development Workshop

Centers for Disease Control and PreventionGlobal Health Odyssey MuseumTom Harkin Global Communications Center June 6-10, 2011

slide3

Teach Epidemiology

Teach Epidemiology

slide4

Teach Epidemiology Web Site

http://www.teachepidemiology.org/

slide6

Epidemiological Case Studies

http://www.cdc.gov/epicasestudies/download_simulation.html

slide7

Epidemiological Case Studies

http://www.cdc.gov/epicasestudies/download_classroom.html

slide8

Heads Up

http://www.cdc.gov/concussion/HeadsUp/youth.html

slide9

US Census Bureau

http://factfinder.census.gov/home/saff/main.html?_lang=en

slide10

MMWR

http://www.cdc.gov/

slide43

Time Check

8:15 AM

slide45

Teach Epidemiology

Teach Epidemiology

slide46

Time Check

8:45 AM

slide48

Teach Epidemiology

Teach Epidemiology

slide49

Teach Epidemiology

EPI-501

Marian R Passannante, PhD

Associate Professor

University of Medicine and Dentistry of New Jersey

New Jersey Medical School

School of Public Health

epidemiology

Enduring Epidemiological Understandings

Epidemiology
  • Descriptive
    • concentrates on examining the distribution of diseases in the population in terms of person, (who gets the disease), place (where they get the disease) and time (when they get the disease)
    • Generates hypotheses

50

Teach Epidemiology

descriptive epidemiology

Enduring Epidemiological Understandings

Descriptive Epidemiology
  • Person

Source: Reported Tuberculosis in the United States, 2009

http://www.cdc.gov/tb/statistics/surv/surv2009/slides/surv9.htm

51

Teach Epidemiology

descriptive epidemiology1
Descriptive Epidemiology

Place

Reference

Hootman JM, Pan L, Helmick CG, Hannan C. State-specific trends in obesity prevalence among adults with arthritis, Behavioral Risk Factor Surveillance System, 2003–2009.MMWR 2011;60(16):509-513.

Enduring Epidemiological Understandings

52

Teach Epidemiology

descriptive epidemiology2

Enduring Epidemiological Understandings

Descriptive Epidemiology
  • Time

 source: http://www.cdc.gov/chronicdisease/resources/publications/aag/osh.htm

53

Teach Epidemiology

epidemiology1

Enduring Epidemiological Understandings

Epidemiology
  • Descriptive
  • Analytic

54

Teach Epidemiology

epidemiologic study designs

Enduring Epidemiological Understandings

Epidemiologic Study Designs

What is the relationship between physical activity and health status among high school students?

  • Define outcome and how it will be measured.
  • Define the exposure and how it will be measured.

55

Teach Epidemiology

epidemiologic study designs1

Enduring Epidemiological Understandings

Epidemiologic Study Designs

What is the relationship between physical activity and health status among high school students?

  • Define outcome and how it will be measured.
  • Health status: absenteeism
  • Define the exposure and how it will be measured.
  • Physical Activity: participation in varsity sports

56

Teach Epidemiology

epidemiologic study designs2

Enduring Epidemiological Understandings

Epidemiologic Study Designs

Ecological Studies

  • Information is collected on groups, not individuals
  • Often called correlation studies
  • Easy to perform- data often already available

57

Teach Epidemiology

epidemiologic study designs3

Enduring Epidemiological Understandings

Epidemiologic Study Designs

Ecological Study

High school

Absenteeism Rate

Number of lost school days due to

absence /(Number of students) x

(Number of schooldays) x 100

% of high school

students on varsity sports teams

58

Teach Epidemiology

epidemiologic study designs4

Enduring Epidemiological Understandings

Epidemiologic Study Designs

Ecological Studies

Advantages

  • Information is collected on groups, not individuals
  • Easy to perform- data often already available

Disadvantages

  • Doesn’t control for other factors (confounders)
  • Individual associations may not be the same as group associations

59

Teach Epidemiology

epidemiology2

Enduring Epidemiological Understandings

Epidemiology
  • Analytic
    • concerned with studying the relationship between an exposure and an outcome
    • test hypotheses
    • Includes a comparison group

60

Teach Epidemiology

analytic epidemiology

Enduring Epidemiological Understandings

Analytic Epidemiology
  • Outcomes
    • Health or Disease outcomes
    • Dependent variable
    • Y variable
  • Exposures
    • Risk or Protective Factor
    • Independent or Predictor variable
    • X variable

61

Teach Epidemiology

epidemiology3

Enduring Epidemiological Understandings

Epidemiology
  • Analytic
    • Observational
      • Cross-Sectional
      • Case-Control
      • Cohort
    • Experimental
      • Behavioral Trials
      • Clinical Trials

63

Teach Epidemiology

epidemiologic study designs5

Enduring Epidemiological Understandings

Epidemiologic Study Designs

Cross-Sectional Studies

Data on possible risk factors and disease outcomes are collected at the same time.

These studies are sometimes called prevalence studies since the information collected can be used to provide prevalence (the proportion in a population with a particular outcome).

64

Teach Epidemiology

epidemiologic study designs6

Enduring Epidemiological Understandings

Epidemiologic Study Designs

How would you measure the exposure and outcome?

Physical Activity Health Status

65

Teach Epidemiology

epidemiologic study designs7

Enduring Epidemiological Understandings

Epidemiologic Study Designs

How would you measure the exposure and outcome?

Physical Activity Health Status

1. Participation in organized sports 1. Days Absent

2. Amount of daily/weekly exercise 2. Body Mass Index

3. Amount of vigorous exercise 3. Blood Pressure

66

Teach Epidemiology

epidemiologic study designs8

Enduring Epidemiological Understandings

Epidemiologic Study Designs

How would you design a cross sectional study of

Physical Activity Health Status

among high school students? Health Status (BMI)

67

Teach Epidemiology

epidemiologic study designs9

Enduring Epidemiological Understandings

Epidemiologic Study Designs

How would you design a cross sectional study of

Physical Activity Health Status

among high school students? Obesity

Conduct a Survey asking

questions about current

Physical activity, height and

Body weight.

68

Teach Epidemiology

epidemiologic study designs10

Enduring Epidemiological Understandings

Epidemiologic Study Designs

How would you design a cross sectional study of

Physical Activity Health Status

among high school students?

Obesity

  • Conduct a Survey
    • Calculate Prevalence of Health Outcome

In both Physical Activity Groups

A/A+B and C/C+D

    • Calculate a Prevalence Ratio to compare groups

(A/A+B)/(C/C+D)

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Teach Epidemiology

epidemiologic study designs11

Enduring Epidemiological Understandings

Epidemiologic Study Designs

How would you design a cross sectional study of

Physical Activity Health Status

among high school students?

Advantages

  • Good for generating prevalence Obese
  • Can be done over a short period of time

Disadvantages

  • Survey data difficult to verify
  • Can not provide information on causal associations
  • Unclear whether exposure or disease came first

(e.g. Are students obese because they are less physically

active or are they less physically active because they are

obese?)

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Teach Epidemiology

epidemiologic study designs12

Enduring Epidemiological Understandings

Epidemiologic Study Designs

How would you design a case-control study of

Physical Activity Health Status

among high school students?

Obesity

1) Identify cases and controls

2) Interview cases and control to ask

about physical activity during the past

4 years

3) Fill in the 2 x 2 table and calculate

The Odds Ratio

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Teach Epidemiology

what is an odds ratio
What is an odds ratio?
  • A measure of association used to quantify the relationship between an exposure and an outcome. It is also called the cross-products ratio.
    • Outcome: obesity
    • Exposure: physical activity
  • The ratio of the odds that cases (obese) were exposed to a particular risk factor (physical activity) as compared with the odds that the controls (non-obese) were exposed to that same risk factor (physical activity).
    • In a case-control study the odds ratio=

Odds that a case was exposed / Odds that a control was exposed

what is an odds ratio1
What is an odds ratio?

Can be calculated using a simple 2-by-2 contingency table.

Odds of that a case was exposed: a/c

Odds of that a control was exposed: b/d

Ratio of the odds or Odds Ratio: (a/c)/(b/d)

= ad/bc (cross-products ratio)

Outcome

Exposure Case Control

yes a b

no c d

epidemiologic study designs13

Enduring Epidemiological Understandings

Epidemiologic Study Designs

How would you design a case-control study of

Physical Activity Health Status

among high school students?

  • Identify those with high and low health status

(# of cases and # controls may or may not be the same)

  • Ask them questions about prior physical activity level
  • Calculate a measure of risk: Odds Ratio

A x D = 12 x 178 = 2136 = .507

B x C 183 x 23 4209

Odds that obese students were physically active were about 50% lower than the odds that non-obese students were physically activity.

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Teach Epidemiology

slide75

Interpretation of the Odds Ratio source: modified from Jekel et al. Epidemiology, Biostatistics and Preventive Medicine, pg 93.

|

|- 4.0 (4/1)

|

|- 2.0 (2/1)

|

|----------------1.0 (1/1)= equal odds in two groups

|

|- 0.5 (1/2)

|

|- 0.25 (1/4)

slide76

Interpretation of the Odds Ratio source: modified from Jekel et al. Epidemiology, Biostatistics and Preventive Medicine, pg 93.

|

|- 4.0 (4/1) Odds that cases were exposed are 4 times higher than

| the odds that controls were exposed

|- 2.0 (2/1) (the exposure is positively related to the disease)

|

|----------------1.0 (1/1)= equal odds in two groups

| (the exposure is not related to the disease )

|- 0.5 (1/2)

|

|- 0.25 (1/4) Odds that cases were exposed are

| 25% as high or 75% lower

l than the odds that controls were exposed

| (the exposure is negatively related to the disease)

epidemiologic study designs14

Enduring Epidemiological Understandings

Epidemiologic Study Designs

How would you design a case-control study of

Physical Activity Health Status

among high school students?

Obesity

  • Advantages
    • Good for studying rare outcomes
    • Do not need very large sample
  • Disadvantages
    • Can not calculate incidence rates
    • Must estimate relative risk using the odds ratio
    • Estimates may be affected by recall bias

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Teach Epidemiology

epidemiologic study designs15

Enduring Epidemiological Understandings

Epidemiologic Study Designs

How would you design a cohort study of

Physical Activity Health Status

among high school students? Obesity

78

Teach Epidemiology

epidemiologic study designs16

Enduring Epidemiological Understandings

Epidemiologic Study Designs

How would you design a cohort study of

Physical Activity Obesity

among high school students? Obesity

1) Identify students with high and low activity level

who are not obese at the start of high school

2) Follow them over time and calculate BMI

3) Calculate Incidence of obesity in both exposure groups

4) Calculate Relative Risk (incidence in exposed group

divided by incidence in unexposed group)

(A/ A+B) / (C/C+D) = 10/500 = .50

20/500

The risk of obesity is 50% lower in those who had high levels of physical activity compare d to those who did not.

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slide80

Interpretation of the Relative Risksource: modified from Jekel et al. Epidemiology, Biostatistics and Preventive Medicine, pg 93.

|

|- 4.0 (4/1) Risk of outcome is 4 times higher among those with the

| factor as compared to those without the factor

|- 2.0 (2/1)

|

|----------------1.0 (1/1)= equal risk in two groups

|

|- 0.5 (1/2)

|

|- 0.25 (1/4) Risk of outcome is 25% as high or 75% lower among

| those with the factor as compared to those without the factor

epidemiologic study designs17

Enduring Epidemiological Understandings

Epidemiologic Study Designs

How would you design a cohort study of

Physical Activity Health Status

among high school students?

  • Advantages Health Status
    • Allow for the direct calculation of incidence rates
    • Good for studying rare exposures
    • Allows investigators to assess the progression from exposure

to disease

  • Disadvantages
    • Need a large sample
    • Can take a long time to complete the study
    • More costly and labor intensive than other studies
    • Those who are lost to follow-up can bias the outcome

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Teach Epidemiology

epidemiologic study designs experimental

Enduring Epidemiological Understandings

Epidemiologic Study Designs Experimental

How would you design a behavioral trial of

Physical Activity Health Status

among high school students? Health Status

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Teach Epidemiology

epidemiologic study designs experimental1

Enduring Epidemiological Understandings

Epidemiologic Study DesignsExperimental

How would you design a behavioral trial of

Physical Activity Health Status

among high school students?

Obesity

  • Random assignment of normal weight students

to different activity level

2) Follow groups over time to calculate incidence of

health status outcome (blind evaluation)

  • Calculate Relative Risk (incidence in exposed group

divided by incidence in unexposed group)

Would this be ethical?

83

Teach Epidemiology

epidemiologic study designs experimental2

Enduring Epidemiological Understandings

Epidemiologic Study DesignsExperimental

How would you design a clinical trial of

Vitamin C Health Status

among high school students?

Health Status

  • Random assignment of healthy to Vitamin C
  • Follow groups over time to calculate incidence of

health status outcome (blind evaluation)

  • Calculate Relative Risk (incidence in exposed group

divided by incidence in unexposed group)

Would this be ethical?

84

Teach Epidemiology

epidemiologic study designs18

Enduring Epidemiological Understandings

Epidemiologic Study Designs

Ethical Issues

  • Minimizing Risks and Maximizing Benefits
  • Informed Consent
  • Confidentiality of information
  • Respect for Human Rights
  • Scientific Integrity

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epidemiologic study designs19

Enduring Epidemiological Understandings

Epidemiologic Study Designs

Ethical Issues

  • Minimizing Risks and Maximizing Benefits
      • Physical
      • Emotional
      • Especially in vulnerable populations

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epidemiologic study designs20

Enduring Epidemiological Understandings

Epidemiologic Study Designs

Ethical Issues

  • Informed Consent
    • Investigators must provide clear and complete information regarding a research project so that potential participants area able to decide whether or not to be part of the study..
  • Source: Coughlin S, Ethical issues in epidemiologic research and public health practice . Emerging Themes in Epidemiology 2006, 3:16 open access

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epidemiologic study designs21

Enduring Epidemiological Understandings

Epidemiologic Study Designs

Ethical Issues

  • Confidentiality of Information
    • Limiting access to study data
    • Study records locked away
    • Limit/delete identifying information on data collection forms and in computer files
    • Encrypting of computer databases
    • Limit geographic detail
  • Source: Coughlin S, Ethical issues in epidemiologic research and public health practice . Emerging Themes in Epidemiology 2006, 3:16 open access

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epidemiologic study designs22

Enduring Epidemiological Understandings

Epidemiologic Study Designs

Ethical Issues

  • Confidentiality of Information
    • Certificate of ConfidentialityCertificates protect against compulsory legal demands, such as court orders and subpoenas, for identifying information or identifying characteristics of a research participant.

Source: http://grants.nih.gov/grants/policy/coc/faqs.htm

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Teach Epidemiology

epidemiologic study designs23

Enduring Epidemiological Understandings

Epidemiologic Study Designs

Ethical Issues

  • Respect for Human Rights
    • Individual rights
    • Right of the Population

90

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epidemiologic study designs24

Enduring Epidemiological Understandings

Epidemiologic Study Designs

Ethical Issues

  • Scientific Integrity
    • Research sponsorship
      • Appearance of conflict of interest
      • Possible conflict of interest
    • Conducting and reporting research honestly

91

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epidemiologic study designs25

Enduring Epidemiological Understandings

Epidemiologic Study Designs

Ethical Issues

The institutional review board system (IRB)

United States, federal regulations to protect human research subjects (45 CFR 46) have resulted in a complex IRB system. Similar safeguards exist in many other countries.

We recommend that students doing epidemiologic research

  • Login to the NIH Protecting Human Research Participants training modules (http://phrp.nihtraining.com/users/login.php).
  • Complete three of the seven training modules; History, Codes and Regulations, and Respect for Persons.

Source: Coughlin S, Ethical issues in epidemiologic research and public health practice . Emerging Themes in Epidemiology 2006, 3:16 open access

92

Teach Epidemiology

epidemiologic study designs break
Epidemiologic Study DesignsBreak

Enduring Epidemiological Understandings

93

Teach Epidemiology

epidemiologic measures of morbidity

Identifying Patterns of Health and Disease and Formulating Hypotheses

Epidemiologic Measures of Morbidity

Incidence refers to the occurrence of new cases of disease or injury in a population over a specified period of time.

Prevalence refers to the proportion of persons in a population who have a particular disease or attribute at a specified point in time or over a specified period of time.

Teach Epidemiology

Source of Definitions: Principles of Epidemiology in Public Health Practice Third Edition , U.S. DHHS, CDC

cross sectional studies
Cross-Sectional Studies

Data on exposure and outcome are collected at the same time.

  • Prevalence Ratio
    • Prevalence of Outcome among those who have the exposure

A/A+B

    • Prevalence of the Outcome among those who did not have the exposure C/C+D
    • Calculate a Prevalence Ratio to compare groups (A/A+B)/(C/C+D)
outcome measures
Outcome measures

Case-Control Study

Odds Ratio = A x D

B x C

aka: Cross-Products Ratio

Cohort study

Relative Risk=

Incidence in Exposed = (A/A+B)

Incidence in Unexposed (C/C+D)

analytic epidemiology2
Analytic Epidemiology

Enduring Epidemiological Understandings

98

Teach Epidemiology

analytic epidemiology4

Enduring Epidemiological Understandings

Analytic Epidemiology

Source: Principles of Epidemiology in Public Health Practice Third Edition , U.S. DHHS, CDC

100

Teach Epidemiology

analytic epidemiology5

Enduring Epidemiological Understandings

Analytic Epidemiology

Answer: A and E

Experimental Clinical Trial

101

Teach Epidemiology

analytic epidemiology6

Enduring Epidemiological Understandings

Analytic Epidemiology

Source: Principles of Epidemiology in Public Health Practice Third Edition , U.S. DHHS, CDC

102

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analytic epidemiology7

Enduring Epidemiological Understandings

Analytic Epidemiology

Answer: A and E

Experimental Clinical Trial

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analytic epidemiology8

Enduring Epidemiological Understandings

Analytic Epidemiology

Source: Principles of Epidemiology in Public Health Practice Third Edition , U.S. DHHS, CDC

104

Teach Epidemiology

analytic epidemiology9

Enduring Epidemiological Understandings

Analytic Epidemiology

Answer: B and C

Observational Cohort Study

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analytic epidemiology10

Enduring Epidemiological Understandings

Analytic Epidemiology

Source: Principles of Epidemiology in Public Health Practice Third Edition , U.S. DHHS, CDC

106

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analytic epidemiology13

Enduring Epidemiological Understandings

Analytic Epidemiology

OR = (32x60) = 12

(8 x 20)

Source: Principles of Epidemiology in Public Health Practice Third Edition , U.S. DHHS, CDC

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analytic epidemiology14

Enduring Epidemiological Understandings

Analytic Epidemiology

What is the appropriate measure of risk?

Calculate this measure.

Source: Principles of Epidemiology in Public Health Practice Third Edition , U.S. DHHS, CDC

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analytic epidemiology15

Enduring Epidemiological Understandings

Analytic Epidemiology

Relative Risk

Incidence of illness in exposed group (those who ate cake) = 50/53 = .943 = 6.1

Incidence of illness in non-exposed group (did not eat cake) 4/26 .154

Source: Principles of Epidemiology in Public Health Practice Third Edition , U.S. DHHS, CDC

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analytic epidemiology16

Enduring Epidemiological Understandings

Analytic Epidemiology

A cross-sectional study was conducted among 1000 high school students. Students were asked to provide information on their gender and whether they had smoked more than 1 cigarette during the past week. The study data are provided in the table below.

What is the prevalence of smoking

Among males? Among Females?

Calculate a Prevalence Ratio.

Teach Epidemiology

analytic epidemiology17

Enduring Epidemiological Understandings

Analytic Epidemiology

A cross-sectional study was conducted among 1000 randomly selected high school students. Students were asked to provide information on their gender and whether they had smoked more than 1 cigarette during the past week. The study data are provided in the table.

What is the prevalence of smoking

Among males? 40/400 = 10%

Among Females? 30/600 = 5%

Prevalence Ratio 10/5 = 2

Teach Epidemiology

what is a confidence interval

Enduring Epidemiological Understandings

What is a Confidence Interval?
  • Confidence intervals can be calculated for many epidemiologic measures including Incidence and Prevalence, Prevalence ratios, Odds Ratios and Relative Risks.
  • A confidence interval tells the reader how much variability there is associated with the measurement.
  • 95% or 99% confidence intervals are often reported in epidemiologic literature around these measurements.

Teach Epidemiology

interpretation of a confidence interval on an odds ratio

Enduring Epidemiological Understandings

Interpretation of a Confidence Interval on an Odds Ratio

If a 95% Confidence Interval on an Odds Ratio excludes 1.0, then we can be 95% sure that the exposure and the disease are related.

If the 95% Confidence Interval includes 1.0, then it is possible that there is no relationship between the exposure and the outcome, because….

Teach Epidemiology

slide118

Interpretation of the Odds Ratio source: modified from Jekel et al. Epidemiology, Biostatistics and Preventive Medicine, pg 93.

|

|- 4.0 (4/1) Odds that cases were exposed are 4 times higher than

| the odds that controls were exposed

|- 2.0 (2/1) (the exposure is positively related to the disease)

|

|----------------1.0 (1/1)= equal odds in two groups

| (the exposure is not related to the disease )

|- 0.5 (1/2)

|

|- 0.25 (1/4) Odds that cases were exposed are

| 25% as high or 75% lower

l than the odds that controls were exposed

| (the exposure is negatively related to the disease)

slide120

Time Check

9:45 AM

slide122

Teach Epidemiology

Teach Epidemiology

slide124

Enduring Epidemiological Understandings

Knowledge that “… is connected and organized, and … ‘conditionalized’ to specify the context in which it is applicable.”

National Research Council , Learning and Understanding

Teach Epidemiology

slide125

Associated

Association Found Between Coffee and Pancreatic Cancer

Teach Epidemiology

slide126

Associated

Tied

Related

Associated

Linked

What do we mean when we say that there is anassociationbetween two things?

Things that are associatedare linked in some way that makes themturn up together.

Teach Epidemiology

slide127

Associated

Things that are associated are linked in some way that makes themturn up together.

Teach Epidemiology

slide128

Associated

Suicide Higher in Areas with Guns

Smoking Linked to Youth Eating Disorders

Family Meals Are Good for Mental Health

Study Links Iron Deficiency to Math Scores

Study Concludes: Movies Influence Youth Smoking

Lack of High School Diploma Tied to US Death Rate

Study Links Spanking to Aggression

Depressed Teens More Likely to Smoke

Snacks Key to Kids’ TV- Linked Obesity: China Study

Breakfast Each Day May Keep Colds Away

Pollution Linked with Birth Defects in US Study

Kids Who Watch R-Rated Movies More Likely to Drink, Smoke

Teach Epidemiology

slide129

Descriptive Epidemiology

Epidemiologic studies that are concerned with characterizing the amount and distribution of health and disease within a population.

Teach Epidemiology

slide130

Analytical Epidemiology

Epidemiologic studies that are concerned with determinants of disease and the reasons for relatively high or low frequencies of disease in specific population subgroups.

Teach Epidemiology

slide131

Formulating

Testing

Descriptive Epidemiology

Analytical Epidemiology

Hypothesis

Hypothesis

An unproven idea, based on observation or reasoning, that can be supported or refuted through investigation

An educated guess

Teach Epidemiology

slide132

Making Group Comparisons and Identifying Associations

Hypothesis:

Buprenorphine will stop heroin addicts from using heroin.

Teach Epidemiology

slide133

Population

Making Group Comparisons and Identifying Associations

Trial 1

slide134

10 Weeks

Making Group Comparisons and Identifying Associations

Trial 1

Population

500 Heroin Addicts

Sample 100 Heroin Addicts

slide135

10 Weeks

Making Group Comparisons and Identifying Associations

Trial 1

Population

500 Heroin Addicts

Sample 100 Heroin Addicts

21 Heroin Addicts Tested Negative for Heroin

slide136

Making Group Comparisons and Identifying Associations

Trial 1

Tested Negative for Heroin

Tested Positive for Heroin

Total

Bupe

21

79

100

Teach Epidemiology

slide137

Making Group Comparisons and Identifying Associations

Lord Kelvin

When you can measure what you are speaking about, and express it in numbers, you know something about it.

But when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meager and unsatisfactory kind.

Teach Epidemiology

slide138

Numerator

Outcome

Making Group Comparisons and Identifying Associations

Risk

A measure of how often an outcome occurs in a defined population in a defined period of time. It consists of a numeratorand a denominator.

Denominator

The numeratoris the number of people in the population or sample who experienced the outcomeand the denominatoris the total number of people in the population or sample.

Population / Sample

Teach Epidemiology

slide139

Making Group Comparisons and Identifying Associations

Risk

Numerator

21 tested negative for heroin

Denominator

100 study subjects

… the risk of a negative heroin test was 21 / 100 in a 10-week period

Teach Epidemiology

slide140

Making Group Comparisons and Identifying Associations

Risk / Rate

A measure of how often an outcome occurs in a defined group of people in a defined period of time.

The likelihood of an outcome occurring.

Teach Epidemiology

slide141

21 %

or

Making Group Comparisons and Identifying Associations

Calculating Risk

Trial 1

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Total

21

Bupe

21

79

100

100

Teach Epidemiology

slide142

Making Group Comparisons and Identifying Associations

Inference

Process of predicting from what is observed in a sample to what is true for the entire population.

Teach Epidemiology

slide143

21 %

or

Making Group Comparisons and Identifying Associations

Inference

Probe

Trial 1

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Total

21

Bupe

21

79

100

100

What does this tell you about the hypothesis?

Buprenorphine will stop heroin addicts from using heroin.

Teach Epidemiology

slide144

Making Group Comparisons and Identifying Associations

Control Group

People who participate in a trial, but do not get the treatment.

People whose results are compared to the group that was treated.

Teach Epidemiology

slide145

21 %

or

Making Group Comparisons and Identifying Associations

Control Group

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Total

21

Bupe

21

79

100

100

Extend and label the table to include a control group.

Teach Epidemiology

slide146

21 %

or

?

? %

or

100

Making Group Comparisons and Identifying Associations

Control Group

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Total

21

Bupe

21

79

100

100

No Bupe

100

Making Group Comparisons

Teach Epidemiology

slide147

Outcome / Disease

Exposure

21 %

or

?

? %

or

100

Making Group Comparisons and Identifying Associations

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Total

a

b

21

Bupe

21

79

100

100

c

d

No Bupe

100

Making Group Comparisons

Teach Epidemiology

slide148

21 %

or

?

? %

or

100

Making Group Comparisons and Identifying Associations

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Total

21

Bupe

21

79

100

100

No Bupe

100

Teach Epidemiology

slide149

Making Group Comparisons and Identifying Associations

Contingency Table

A cross-classification of data where categories of one variable are presented in rows and categories of another variable are presented in columns

The simplest contingency table is the 2x2 table.

Teach Epidemiology

slide150

10 Weeks

Making Group Comparisons and Identifying Associations

Trial 1

Population

500 Heroin Addicts

Sample 100 Heroin Addicts

21 Heroin Addicts Tested Negative for Heroin

slide151

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Total

?

? %

Bupe

100

100

a b

c d

?

No Bupe

100

? %

100

Making Group Comparisons and Identifying Associations

Trial 2

Teach Epidemiology

slide152

O

E

O

Assigned

O

E

O

Making Group Comparisons and Identifying Associations

Volunteer Heroin Addicts

Teach Epidemiology

slide153

21

21%

21

79

100

or

100

Making Group Comparisons and Identifying Associations

Trial 2

Probe

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Total

Bupe

a b

c d

No Bupe

Teach Epidemiology

slide154

21

21

21%

21%

21

21

79

79

100

100

or

or

100

100

Making Group Comparisons and Identifying Associations

Trial 2

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Total

Bupe

a b

c d

No Bupe

Teach Epidemiology

slide155

21

21

21%

21%

21

21

79

79

100

100

or

or

100

100

Making Group Comparisons and Identifying Associations

Trial 2

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Total

Bupe

a b

c d

No Bupe

Inference: Process of predicting from what is observed in a sample to what is occurring in the entire population

Teach Epidemiology

slide156

Making Group Comparisons and Identifying Associations

Lord Kelvin

When you can measure what you are speaking about, and express it in numbers, you know something about it.

But when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meager and unsatisfactory kind.

Teach Epidemiology

slide157

Making Group Comparisons and Identifying Associations

Ratio

The value obtained by dividing one quantity by another

Teach Epidemiology

slide158

Risk Ratio

21

21

21%

21%

21

21

79

79

100

100

or

or

100

100

Making Group Comparisons and Identifying Associations

Trial 2

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Total

Bupe

a b

c d

1

No Bupe

Ratio: The value obtained by dividing one quantity by another

Risk Ratio: The ratio of two risks

Teach Epidemiology

slide159

Risk Ratio

a

21

21

21%

21%

21

21

79

79

100

100

or

or

a + b

100

100

c

c + d

Making Group Comparisons and Identifying Associations

Create a formula

Trial 2

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Total

Bupe

a b

c d

1

No Bupe

Ratio: The value obtained by dividing one quantity by another

Risk Ratio: The ratio of two risks

Teach Epidemiology

slide160

Risk Ratio

21

21

21%

21%

21

21

79

79

100

100

or

or

100

100

Making Group Comparisons and Identifying Associations

Trial 2

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Relative Risk

Total

Bupe

a b

c d

1

No Bupe

Relative Risk: The ratio of the risk of an outcome among the exposed to the risk of the outcome among the unexposed.

Teach Epidemiology

slide161

Risk Ratio

21

21

21%

21%

21

21

79

79

100

100

or

or

100

100

Making Group Comparisons and Identifying Associations

Trial 2

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Relative Risk

Total

Bupe

a b

c d

1

No Bupe

Inference: Process of predicting from what is observed in a sample to what is occurring in the entire population

The inference here is that there is no effect of Buprenorphine

Teach Epidemiology

slide162

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Total

?

Bupe

? %

100

or

100

a b

c d

?

No Bupe

? %

100

or

100

Making Group Comparisons and Identifying Associations

Trial 3

Teach Epidemiology

slide163

21

21%

21

79

100

or

100

Making Group Comparisons and Identifying Associations

Trial 3

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Total

Bupe

a b

c d

No Bupe

Teach Epidemiology

slide164

21

62

21%

62%

21

62

79

38

100

100

or

or

100

100

Making Group Comparisons and Identifying Associations

Trial 3

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Total

Bupe

a b

c d

No Bupe

Teach Epidemiology

slide165

21

62

62%

21%

21

62

79

38

100

100

or

or

100

100

Making Group Comparisons and Identifying Associations

Trial 3

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Total

Bupe

a b

c d

No Bupe

Inference: Process of predicting from what is observed in a sample to what is occurring in the entire population

Teach Epidemiology

slide166

21

62

21%

62%

62

21

38

79

100

100

or

or

100

100

Making Group Comparisons and Identifying Associations

Trial 3

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Relative Risk

Total

Bupe

a b

c d

0.34

No Bupe

Relative Risk: The ratio of the risk of an outcome among the exposed to the risk of the outcome among the unexposed.

Teach Epidemiology

slide167

21

62

21%

62%

62

21

38

79

100

100

or

or

100

100

Making Group Comparisons and Identifying Associations

Trial 3

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Relative Risk

Total

Bupe

a b

c d

0.34

No Bupe

0.34

The heroin addicts who received Bupe were ___ times as likely to test negative for heroin as those who did not receive Bupe.

Teach Epidemiology

slide168

21

62

21%

62%

62

21

38

79

100

100

or

or

100

100

Making Group Comparisons and Identifying Associations

Trial 3

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Relative Risk

Total

Bupe

a b

c d

0.34

No Bupe

Inference: Process of predicting from what is observed in a sample to what is occurring in the entire population.

Teach Epidemiology

slide169

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Total

?

Bupe

? %

100

or

100

a b

c d

?

No Bupe

? %

100

or

100

Making Group Comparisons and Identifying Associations

Trial 4

Teach Epidemiology

slide170

21

21%

21

79

100

or

100

Making Group Comparisons and Identifying Associations

Trial 4

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Total

Bupe

a b

c d

No Bupe

Teach Epidemiology

slide171

21

6

21%

6%

21

6

79

94

100

100

or

or

100

100

Making Group Comparisons and Identifying Associations

Trial 4

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Total

Bupe

a b

c d

No Bupe

Teach Epidemiology

slide172

21

6

21%

6%

6

21

94

79

100

100

or

or

100

100

Making Group Comparisons and Identifying Associations

Trial 4

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Relative Risk

Total

Bupe

a b

c d

3.5

No Bupe

Relative Risk: The ratio of the risk of an outcome among the exposed to the risk of the outcome among the unexposed.

Teach Epidemiology

slide173

21

6

21%

6%

6

21

94

79

100

100

or

or

100

100

Making Group Comparisons and Identifying Associations

Trial 4

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Relative Risk

Total

Bupe

a b

c d

3.5

No Bupe

3.5

The heroin addicts who received Bupe were ___ times as likely to test negative for heroin as those who did not receive Bupe.

Teach Epidemiology

slide174

21

6

21%

6%

6

21

94

79

100

100

or

or

100

100

Making Group Comparisons and Identifying Associations

Trial 4

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Relative Risk

Total

Bupe

a b

c d

3.5

No Bupe

Inference: Process of predicting from what is observed in a sample to what is occurring in the entire population.

Teach Epidemiology

slide175

21

21%

21

79

100

or

100

Making Group Comparisons and Identifying Associations

Trial 1

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Total

Bupe

Nothing

What do the results tell us about the hypothesis that Buprenorphine will stop heroin addicts from using heroin?

Teach Epidemiology

slide176

Making Group Comparisons and Identifying Associations

Trial 1

Trial 2

Trial 3

Trial 4

Teach Epidemiology

slide177

21

90

21%

21

79

100

or

100

Making Group Comparisons and Identifying Associations

Trial 1

Trial 2

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Total

Bupe

Nothing

Trial 3

Trial 4

Teach Epidemiology

slide178

21

90

21%

21

79

100

or

100

Making Group Comparisons and Identifying Associations

Trial 1

Trial 2

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Relative Risk

Total

Total

Bupe

Bupe

No Bupe

Nothing

Trial 3

Trial 4

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Relative Risk

Relative Risk

Total

Total

Bupe

Bupe

No Bupe

No Bupe

Teach Epidemiology

slide179

21

21

21

21

90

90

90

90

21%

21%

21%

21%

21

21

21

21

79

79

79

79

100

100

100

100

or

or

or

or

100

100

100

100

Making Group Comparisons and Identifying Associations

Trial 1

Trial 2

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Relative Risk

Total

Total

Bupe

Bupe

No Bupe

Nothing

Trial 3

Trial 4

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Relative Risk

Relative Risk

Total

Total

Bupe

Bupe

No Bupe

No Bupe

Teach Epidemiology

slide180

21

21

21

21

21

90

90

90

90

90

21%

21%

21%

21%

21%

21

21

21

21

21

79

79

79

79

79

100

100

100

100

100

or

or

or

or

or

100

100

100

100

100

Making Group Comparisons and Identifying Associations

Trial 1

Trial 2

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Relative Risk

Total

Total

Bupe

Bupe

1

No Bupe

Bupe is not associated with having a negative test for heroin.

Nothing

Trial 3

Trial 4

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Relative Risk

Relative Risk

Total

Total

Bupe

Bupe

No Bupe

No Bupe

Teach Epidemiology

slide181

21

62

21

21

21

21

90

90

90

90

90

90

62%

21%

21%

21%

21%

21%

21

21

21

62

21

21

79

79

38

79

79

79

100

100

100

100

100

100

or

or

or

or

or

or

100

100

100

100

100

100

Making Group Comparisons and Identifying Associations

Trial 1

Trial 2

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Relative Risk

Total

Total

Bupe

Bupe

1

No Bupe

Bupe is not associated with having a negative test for heroin.

Nothing

Trial 3

Trial 4

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Relative Risk

Relative Risk

Total

Total

Bupe

Bupe

.34

No Bupe

No Bupe

Bupe is associated with having a positive test for heroin!

Teach Epidemiology

slide182

21

21

62

21

21

6

21

90

90

90

90

90

90

90

21%

21%

21%

21%

62%

6%

21%

62

21

21

21

6

21

21

79

94

79

79

79

38

79

100

100

100

100

100

100

100

or

or

or

or

or

or

or

100

100

100

100

100

100

100

Making Group Comparisons and Identifying Associations

Trial 1

Trial 2

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Relative Risk

Total

Total

Bupe

Bupe

1

No Bupe

Bupe is not associated with having a negative test for heroin.

Nothing

Trial 3

Trial 4

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Relative Risk

Relative Risk

Total

Total

Bupe

Bupe

.34

3.5

No Bupe

No Bupe

Bupe is associated with having a positive test for heroin!

Bupe is associated with having a negative test for heroin.

Teach Epidemiology

slide183

21

21

62

21

21

6

21

90

90

90

90

90

90

90

21%

21%

21%

21%

62%

6%

21%

21

62

21

21

21

6

21

79

79

94

38

79

79

79

100

100

100

100

100

100

100

or

or

or

or

or

or

or

100

100

100

100

100

100

100

Making Group Comparisons and Identifying Associations

Trial 1

Trial 2

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Relative Risk

Total

Total

Bupe

Bupe

1

Nothing

No Bupe

Bupe is not associated with having a negative test for heroin.

Nothing

Trial 3

Trial 4

Compared to what?

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Tested Negative for Heroin

Tested Positive for Heroin

Risk of Negative Heroin Test

Relative Risk

Relative Risk

Total

Total

Bupe

Bupe

.34

3.5

No Bupe

No Bupe

Bupe is associated with having a positive test for heroin!

Bupe is associated with having a negative test for heroin.

Teach Epidemiology

slide184

Buprenorphine

Buprenorphine & Naloxone

Placebo

Making Group Comparisons and Identifying Associations

Handout

Teach Epidemiology

slide185

Enduring Epidemiological Understandings

Knowledge that “… is connected and organized, and … ‘conditionalized’ to specify the context in which it is applicable.”

National Research Council , Learning and Understanding

Teach Epidemiology

slide186

Time Check

10:15 AM

slide188

Teach Epidemiology

Teach Epidemiology

slide189

Time Check

10:30 AM

slide191

Teach Epidemiology

Teach Epidemiology

slide192

In the News

Suicide Higher in Areas with Guns

Smoking Linked to Youth Eating Disorders

Family Meals Are Good for Mental Health

Study Links Iron Deficiency to Math Scores

Study Concludes: Movies Influence Youth Smoking

Lack of High School Diploma Tied to US Death Rate

Study Links Spanking to Aggression

Depressed Teens More Likely to Smoke

Snacks Key to Kids’ TV- Linked Obesity: China Study

Breakfast Each Day May Keep Colds Away

Pollution Linked with Birth Defects in US Study

Kids Who Watch R-Rated Movies More Likely to Drink, Smoke

slide193

2 x 2 Table

Suicide Higher in Areas with Guns

Total

a

b

c

d

slide194

2 x 2 Table

Suicide Higher in Areas with Guns

No Suicide

Suicide

Total

a

b

Areas with Guns

a

b

c

d

Areas without Guns

People who are exposed

slide195

2 x 2 Table

Kids Who Watch R-Rated Movies More Likely to Drink, Smoke

Total

a

b

c

d

slide196

2 x 2 Table

Kids Who Watch R-Rated Movies More Likely to Drink, Smoke

Drink & Smoke

No Drink & Smoke

Total

R-Rated Movies

a

b

c

d

No R-Rated Movies

slide197

2 x 2 Table

Kids Who Watch R-Rated Movies More Likely to Drink, Smoke

Drink & Smoke

No Drink & Smoke

Total

a

R-Rated Movies

a

b

c

d

No R-Rated Movies

People who are exposed and have the outcome

slide198

2 x 2 Table

Family Meals Are Good for Mental Health

Total

a

b

c

d

slide199

2 x 2 Table

Family Meals Are Good for Mental Health

No Mental Health

Mental Health

Total

Family Meals

a

b

c

d

No Family Meals

slide200

2 x 2 Table

Family Meals Are Good for Mental Health

No Mental Health

Mental Health

Total

Family Meals

a

b

c

d

d

No Family Meals

People who are not exposed and do not have the outcome

slide201

2 x 2 Table

Study Links Iron Deficiency to Math Scores

Total

a

b

c

d

slide202

2 x 2 Table

Study Links Iron Deficiency to Math Scores

Poor Math Scores

Good Math Scores

Total

Iron Deficiency

a

b

c

d

No Iron Deficiency

slide203

2 x 2 Table

Study Links Iron Deficiency to Math Scores

Poor Math Scores

Good Math Scores

Total

Iron Deficiency

a

b

c

d

d

No Iron Deficiency

People who do not have the outcome and are not exposed

slide204

2 x 2 Table

Pollution Linked with Birth Defects in US Study

Total

a

b

c

d

slide205

2 x 2 Table

Pollution Linked with Birth Defects in US Study

No Birth Defects

Birth Defects

Total

Pollution

a

b

c

d

No Pollution

slide206

2 x 2 Table

Pollution Linked with Birth Defects in US Study

No Birth Defects

Birth Defects

Total

Pollution

a

b

c

c

d

d

No Pollution

People who are not exposed

slide207

2 x 2 Table

Depressed Teens More Likely to Smoke

Total

a

b

c

d

slide208

2 x 2 Table

Depressed Teens More Likely to Smoke

No Smoke

Smoke

Total

b

Depression

a

b

c

d

d

No Depression

People who do not have the outcome

slide209

2 x 2 Table

Smoking Linked to Youth Eating Disorders

Total

a

b

c

d

slide210

2 x 2 Table

Smoking Linked to Youth Eating Disorders

No Eating Disorders

Eating Disorders

Total

Smoke

a

b

c

d

No Smoke

slide211

2 x 2 Table

Smoking Linked to Youth Eating Disorders

No Eating Disorders

Eating Disorders

Total

b

Smoke

a

b

c

d

No Smoke

People who are exposed and do not have the outcome

slide212

2 x 2 Table

Study Links Spanking to Aggression

Total

a

b

c

d

slide213

2 x 2 Table

Study Links Spanking to Aggression

No Aggression

Aggression

Total

a

Spanking

a

b

c

c

d

No Spanking

People who have the outcome

slide214

2 x 2 Table

Snacks Key to Kids’ TV-Linked Obesity – China Study

Total

a

b

c

d

slide215

2 x 2 Table

Snacks Key to Kids’ TV-Linked Obesity – China Study

No Obesity

Obesity

Total

Snacks

a

b

c

c

d

No Snacks

People who are not exposed and have the outcome

slide217

Enduring Epidemiological Understandings

Knowledge that “… is connected and organized, and … ‘conditionalized’ to specify the context in which it is applicable.”

National Research Council , Learning and Understanding

Teach Epidemiology

slide220

Making Group Comparisons and Identifying Associations

Natural Experiment

Naturally occurring circumstances in which groups of people within a population have been exposed to different levels of the hypothesized cause of an outcome.

220

Teach Epidemiology

slide221

Making Group Comparisons and Identifying Associations

Observational Study

An epidemiologic study of a natural experiment in which the investigator is not involved in the intervention other than to record, classify, count, and statistically analyze results.

221

Teach Epidemiology

slide222

Making Group Comparisons and Identifying Associations

Controlled Trial

An epidemiologic experiment in which subjects are assigned into groups to receive or not receive a hypothesized beneficial intervention.

222

Teach Epidemiology

slide223

Making Group Comparisons and Identifying Associations

Buprenorphine

Buprenorphine will stop heroin addicts from using heroin.

Teach Epidemiology

slide224

Making Group Comparisons and Identifying Associations

Observational Study of a Natural Experiment

Naturally occurring circumstances in which groups of people within a population have been exposed to different levels of the hypothesized cause of an outcome.

Epidemiologic studies of natural experiments in which the investigator is not involved in the intervention other than to record, classify, count, and statistically analyze results.

224

Teach Epidemiology

slide227

Making Group Comparisons and Identifying Associations

Absolutely nothing in the available arsenal of anti-emetics worked at all. I was miserable and came to dread the frequent treatments with an almost perverse intensity. I had heard that marijuana often worked well against nausea. I was reluctant to try it because I had never smoked any substance habitually (and didn’t even know how to inhale). Moreover, I had tried marijuana twice (in the 1960s) … and had hated it …. Marijuana worked like a charm …. The sheer bliss of not experiencing nausea - and not having to fear it for all the days intervening between treatments - was the greatest boost I received in all my year of treatment, and surely the most important effect upon my eventual cure.

Stephen Jay Gould (survivor of abdominal mesothelioma)

227

Teach Epidemiology

slide228

Making Group Comparisons and Identifying Associations

Anecdote

A particular or detached incident or fact of an interesting nature; a biographical incident or fragment; a single passage of private life.

228

Teach Epidemiology

slide229

Science

Making Group Comparisons and Identifying Associations

Transforming Anecdote to Science

Anecdote

229

Teach Epidemiology

slide230

DZ

DZ

E

DZ

E

Healthy People

DZ

E

DZ

DZ

Random Assignment

Healthy People

Healthy People

DZ

DZ

E

E

-

-

-

-

DZ

E

DZ

Healthy People

DZ

DZ

E

E

E

E

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Time

Time

Time

Time

Making Group Comparisons and Identifying Associations

Case-Control Study

Controlled Trial

Cohort Study

Cross-Sectional Study

230

Teach Epidemiology

slide231

DZ

DZ

E

DZ

E

Healthy People

DZ

E

DZ

DZ

Random Assignment

Healthy People

Healthy People

DZ

DZ

E

E

-

-

-

-

DZ

E

DZ

Healthy People

DZ

DZ

E

E

E

E

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Time

Time

Time

Time

Making Group Comparisons and Identifying Associations

Case-Control Study

Controlled Trial

a

b

d

c

Cohort Study

Cross-Sectional Study

231

Teach Epidemiology

slide232

Making Group Comparisons and Identifying Associations

The goal of every epidemiological study is to harvest valid and precise information about the relationship between an exposure and a disease in a population.

The various study designs merely represent different ways of harvesting this information.

Essentials in Epidemiology in Public Health

Ann Aschengrau and George R. Seage III

Teach Epidemiology

slide233

Time Check

11:30 AM

slide235

Teach Epidemiology

Teach Epidemiology

slide236

Time Check

12:30 PM

slide238

Teach Epidemiology

Teach Epidemiology

slide240

The Journey

The Journey

Detectives in the Classroom - Investigation 2-6: The Journey

slide241

Analogy

Detectives in the Classroom - Investigation 2-6: The Journey

slide242

Epi Talk

Epi Talk

Study Design

Procedures and methods, established beforehand, that are followed by the investigator conducting the study.

Detectives in the Classroom - Investigation 2-6: The Journey

slide243

When does the epidemiologist start to observe the journey?

-

When are the passengers identified as exposed or unexposed?

Timing

E

When are the passengers identified as sick or not sick?

DZ

Timing

Detectives in the Classroom - Investigation 2-6: The Journey

slide244

-

Label the Train Tracks

E

DZ

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Time

Detectives in the Classroom - Investigation 2-6: The Journey

slide245

-

Label the Train Tracks

Study Design:

Controlled Trial

E

DZ

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Time

Detectives in the Classroom - Investigation 2-6: The Journey

slide246

DZ

E

DZ

Random Assignment

Healthy People

DZ

E

-

DZ

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Time

Flow Diagram

Flow Diagram

Controlled Trial

Healthy People

Detectives in the Classroom - Investigation 2-6: The Journey

slide247

Label the Train Tracks

Study Design:

Cohort Study

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Time

Detectives in the Classroom - Investigation 2-6: The Journey

slide248

Label the Train Tracks

Cohort Study

Just as in the controlled trial, the epidemiologist is also on the train during the entire journey. But there is an important difference. The epidemiologist is not telling passengers what to do. Rather, the epidemiologist is just observing them and counting. Passengers are not being told to have or not have an exposure, they are just living their normal lives. The epidemiologist, on the ride for the whole journey, just keeps observing everyone’s exposures and whether or not they develop the disease during the journey.

Detectives in the Classroom - Investigation 2-6: The Journey

slide249

-

Label the Train Tracks

Study Design:

Cohort Study

E

DZ

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Time

Detectives in the Classroom - Investigation 2-6: The Journey

slide250

DZ

E

DZ

Healthy People

DZ

E

-

DZ

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Time

Flow Diagram

Flow Diagram

Cohort Study

Healthy People

Detectives in the Classroom - Investigation 2-6: The Journey

slide251

DZ

E

DZ

Healthy People

DZ

E

-

DZ

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Time

Flow Diagram

Flow Diagram

Controlled Trial

Cohort Study

Healthy People

Detectives in the Classroom - Investigation 2-6: The Journey

slide252

DZ

E

DZ

Healthy People

DZ

E

-

DZ

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Time

Flow Diagram

Flow Diagram

Controlled Trial

Cohort Study

Random Assignment

Healthy People

Detectives in the Classroom - Investigation 2-6: The Journey

slide253

Review

Epi Talk

Observational Studies

Epidemiologic studies of natural experiments in which the investigator is not involved in the intervention other than to record, classify, count, and statistically analyze results.

Detectives in the Classroom - Investigation 2-6: The Journey

slide254

Label the Train Tracks

Study Design:

Case-Control Study

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Time

Detectives in the Classroom - Investigation 2-6: The Journey

slide255

Label the Train Tracks

Case-Control Study

The epidemiologist is not on the journey. Rather, the epidemiologist is waiting at the train station at the end of the journey. As passengers get off the train, the epidemiologist selects sick passengers for the case group and selects passengers who are similar but not sick for the control group. The epidemiologist then asks each person in the case group and control group questions about their exposures during the train ride. The epidemiologist relies on passengers’ memories of their exposures that occurred during the train ride.

Detectives in the Classroom - Investigation 2-6: The Journey

slide256

-

Label the Train Tracks

Study Design:

Case-Control Study

DZ

E

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Time

Detectives in the Classroom - Investigation 2-6: The Journey

slide257

E

DZ

E

E

-

DZ

E

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Time

Flow Diagram

Flow

Diagram

Case-ControlStudy

Observational Study

Detectives in the Classroom - Investigation 2-6: The Journey

slide258

Label the Train Tracks

Study Design:

Cross-Sectional Study

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Time

Detectives in the Classroom - Investigation 2-6: The Journey

slide259

Label the Train Tracks

Cross-Sectional Study

The epidemiologist, who has not been on the journey, stops the train somewhere during the trip (kind of like a train robbery) and takes a “snapshot” of all the passengers by asking them whether or not they have the exposure and whether or not they have the disease. Then the epidemiologist leaves the train and goes home to analyze the data from that particular day. The journey continues without the epidemiologist.

Detectives in the Classroom - Investigation 2-6: The Journey

slide260

E

DZ

-

Label the Train Tracks

Study Design:

Cross-Sectional Study

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Time

Detectives in the Classroom - Investigation 2-6: The Journey

slide261

DZ

DZ

E

-

E

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Time

Flow Diagram

Flow

Diagram

Cross-SectionalStudy

Observational Study

Detectives in the Classroom - Investigation 2-6: The Journey

slide262

Epi Talk

Epi Talk

Controlled Trial

An epidemiologic experiment in which subjects are assigned into groups to receive or not receive a hypothesized beneficial intervention.

Detectives in the Classroom - Investigation 2-6: The Journey

slide263

Epi Talk

Epi Talk

Cohort Study

An analytical epidemiological study design in which the investigator selects a group of exposed individuals and a group of unexposed individuals and follows both groups to compare the frequency with which the disease occurs in each group.

Detectives in the Classroom - Investigation 2-6: The Journey

slide264

Epi Talk

Epi Talk

Case-Control Study

An analytical epidemiological study design in which the investigator selects a group of individuals with a disease (cases) and a group of similar individuals without the disease (controls) and compares the frequency with which an exposure occurred in the cases versus the controls.

Detectives in the Classroom - Investigation 2-6: The Journey

slide265

Epi Talk

Epi Talk

Cross-Sectional Study

An analytical epidemiological study design in which the investigator selects a group of individuals and determines the presence or absence of a disease and the presence or absence of an exposure at the same time.

Detectives in the Classroom - Investigation 2-6: The Journey

slide267

Ms. Wilson

After-School, Make-Up Homework Hall

slide268

a

b

c

d

Talking too much on a cell phone causes students not to do their homework.

Label the 2x2 Table

slide269

Talking too much on a cell phone causes students not to do their homework.

Did Not Do Homework

Did Homework

Had Cell Phone

a

b

c

d

Did Not Have Cell Phone

Total

slide270

Talking too much on a cell phone causes students not to do their homework.

Did Not Do Homework

Did Homework

Had Cell Phone

Place the data into the 2x2 Table

a

b

c

d

Did Not Have Cell Phone

Total

slide271

Talking too much on a cell phone causes students not to do their homework.

Did Not Do Homework

Did Homework

Had Cell Phone

15

a

b

c

d

Did Not Have Cell Phone

5

20

Total

slide272

Talking too much on a cell phone causes students not to do their homework.

Did Not Do Homework

Did Homework

Had Cell Phone

15

a

b

c

d

Did Not Have Cell Phone

5

20

Total

Which of the following statements can be made based on the above data:

A: 15 of 20 students, who did not do their homework, had cell phones.

B: 15 of 20 students, who had cell phones, did not do their homework.

slide273

Cohort Study – The Nurses’ Health Study (1976)

Risk

No Connective Tissue Disease

Connective Tissue Disease

Total

Breast Implants

3

1,180

1,183

No Breast Implants

513

85,805

86,318

Which of the following statements can be made based on the above data:

A: 15 of 20 students, who did not do their homework, had cell phones.

B: 15 of 20 students, who had cell phones, did not do their homework.

slide274

Talking too much on a cell phone causes students not to do their homework.

Risk

X

Did Not Do Homework

Did Homework

Odds

Had Cell Phone

15

a

b

c

d

Did Not Have Cell Phone

5

20

Total

Which of the following statements can be made based on the above data:

A: 15 of 20 students, who did not do their homework, had cell phones.

B: 15 of 20 students, who had cell phones, did not do their homework.

slide275

Talking too much on a cell phone causes students not to do their homework.

Odds

A ratio of the probability of occurrence of an event to that of its nonoccurrence.

slide276

Odds

Talking too much on a cell phone causes students not to do their homework.

Did Not Do Homework

Did Homework

Had Cell Phone

15

A ratio of the probability of occurrence of an event to that of its nonoccurrence.

a

b

c

d

Did Not Have Cell Phone

5

15 to 5 or 3 to 1

20

Total

Which of the following statements can be made based on the above data:

A: 15 of 20 students, who did not do their homework, had cell phones.

B: 15 of 20 students, who had cell phones, did not do their homework.

slide277

Odds

Talking too much on a cell phone causes students not to do their homework.

Did Not Do Homework

Did Homework

Had Cell Phone

15

A ratio of the probability of occurrence of an event to that of its nonoccurrence.

Nothing

a

b

Compared to what?

c

d

Did Not Have Cell Phone

5

15 to 5 or 3 to 1

20

Total

Which of the following statements can be made based on the above data:

A: 15 of 20 students, who did not do their homework, had cell phones.

B: 15 of 20 students, who had cell phones, did not do their homework.

slide278

Count

Divide

Compare

Talking too much on a cell phone causes students not to do their homework.

slide279

Odds

Talking too much on a cell phone causes students not to do their homework.

Did Not Do Homework

Did Homework

Had Cell Phone

15

A ratio of the probability of occurrence of an event to that of its nonoccurrence.

Nothing

a

b

Compared to what?

c

d

Did Not Have Cell Phone

5

What did Ms. Wilson do?

15 to 5 or 3 to 1

20

Total

Which of the following statements can be made based on the above data:

A: 15 of 20 students, who did not do their homework, had cell phones.

B: 15 of 20 students, who had cell phones, did not do their homework.

slide280

Talking too much on a cell phone causes students not to do their homework.

What did Ms. Wilson do?

slide281

Talking too much on a cell phone causes students not to do their homework.

Place the data into the 2x2 Table

Did Not Do Homework

Did Homework

Had Cell Phone

15

10

a

b

c

d

Did Not Have Cell Phone

5

30

10 to 30 or 1 to 3

20

40

Total

3 to 1

slide282

Talking too much on a cell phone causes students not to do their homework.

Did Not Do Homework

Did Homework

Had Cell Phone

15

10

a

b

c

d

Did Not Have Cell Phone

5

30

10 to 30 or 1 to 3

20

40

Total

3 to 1

What mathematical computation would allow them to complete the statement:

The odds of having a cell phone were ____ times greater among students who had not done their homework compared to students who did do their homework.

slide283

Talking too much on a cell phone causes students not to do their homework.

Did Not Do Homework

Did Homework

Had Cell Phone

15

10

a

b

c

d

Did Not Have Cell Phone

5

30

10 to 30 or 1 to 3

20

40

Total

3 to 1

3 / .33 = 9

3 / 1 = 3

1 / 3 = .33

What mathematical computation would allow them to complete the statement:

The odds of having a cell phone were ____ times greater among students who had not done their homework compared to students who did do their homework.

9

slide284

Talking too much on a cell phone causes students not to do their homework.

Odds Ratio

Ratio of odds in favor of exposure among cases to the odds in favor of exposure among controls.

Relative Odds

slide285

Talking too much on a cell phone causes students not to do their homework.

Did Not Do Homework

Did Homework

Had Cell Phone

15

35

a

b

Odds Ratio

c

d

Did Not Have Cell Phone

5

5

20

40

Total

What mathematical computation would allow them to complete the statement:

The odds of having a cell phone were ____ times greater among students who had not done their homework compared to students who did do their homework.

.43

slide286

Talking too much on a cell phone causes students not to do their homework.

Did Not Do Homework

Did Homework

Had Cell Phone

15

30

a

b

Odds Ratio

c

d

Did Not Have Cell Phone

5

10

20

40

Total

What mathematical computation would allow them to complete the statement:

The odds of having a cell phone were ____ times greater among students who had not done their homework compared to students who did do their homework.

1

slide288

Case-Control Study

Arthur Herbst, et al. “Adenocarcinoma of the Vagina,” New England Journal of Medicine, 284:16, 1971, 878-881

slide295

7

1

8

Case-Control Study

_

DZ

DZ

DZ

X

_

X

slide296

Case-Control Study

_

DZ

DZ

DZ

X

3

_

X

5

8

slide297

Case-Control Study

_

DZ

DZ

DZ

X

6

_

X

2

8

slide298

Case-Control Study

_

DZ

DZ

DZ

X

7

_

X

1

8

slide299

Case-Control Study

_

DZ

DZ

DZ

X

3

_

X

5

8

slide300

Case-Control Study

_

DZ

DZ

DZ

X

1

_

X

7

8

slide302

Case-Control Study

_

DZ

DZ

DZ

X

7

21

_

X

1

11

8

32

slide303

Case-Control Study

_

DZ

DZ

DZ

X

3

1

_

X

5

31

8

32

slide304

Case-Control Study

_

DZ

DZ

DZ

X

6

5

_

X

2

27

8

32

slide305

Case-Control Study

_

DZ

DZ

DZ

X

7

0

_

X

1

32

8

32

slide306

Case-Control Study

_

DZ

DZ

DZ

X

3

3

_

X

5

29

8

32

slide307

Case-Control Study

_

DZ

DZ

DZ

X

1

4

_

X

7

28

8

32

slide311

Epi Team Challenge

Epi Team Challenge

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide312

Cross-Sectional Study

Cohort Study

Case-Control Study

Controlled Trial

DZ

DZ

E

DZ

DZ

E

E

DZ

E

DZ

DZ

Random Assignment

Healthy People

Healthy People

Healthy People

Healthy People

DZ

DZ

E

E

E

-

-

-

-

E

DZ

DZ

DZ

E

E

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Time

Time

Time

Time

What’s My Design?

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide313

Assign treatment and control groups.

Give exposure to treatment group, but not control group.

Follow through time and compare risk of disease in treatment group with risk of disease in control group.

Epidemiologist is involved during the entire time from exposure to disease.

What’s My Design?

Practice Clue

Trial

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide314

What’s My Design?

Begin Epi Team Challenge

Clue 1

Assign treatment and control groups.

Trial

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide315

E

Flow

Diagram

DZ

E

E

Observational Study

-

DZ

E

What’s My Design?

Clue 2

Case-Control Study

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide316

What’s My Design?

Clue 3

Observational Study

Cohort, Case-Control, and Cross-Sectional Studies

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide317

What’s My Design?

Clue 4

Follow through time and compare risk of disease in exposed group with risk of disease in the unexposed group.

Trial and Cohort Study

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide318

Follow through time and compare risk of disease in treatment group with risk of disease in control group.

Give exposure to treatment group, but not control group.

What’s My Design?

Clue 5

Trial

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide319

What’s My Design?

Clue 6

Epidemiologist is involved during the entire time from exposure to disease.

Trial and Cohort Study

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide320

What’s My Design?

Clue 7

Select a group of people with disease and a similar group of people without disease.

Case-Control Study

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide321

Flow Diagram

Non-Observational Study

E

Random Assignment

Healthy People

Healthy People

E

-

What’s My Design?

Clue 8

Trial

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide322

DZ

Flow

Diagram

DZ

E

Observational Study

-

E

What’s My Design?

Clue 9

Cross Sectional Study

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide323

What’s My Design?

Clue 10

Compare odds of exposure in the two groups.

Case-Control Study

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide324

DZ

Flow Diagram

E

DZ

Random Assignment

Healthy People

Healthy People

DZ

E

-

DZ

What’s My Design?

Clue 11

Trial

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide325

What’s My Design?

Clue 12

Flow

Diagram

Cross Sectional Study

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide326

DZ

DZ

DZ

DZ

What’s My Design?

Clue 13

Flow Diagram

Observational Study

Cohort Study

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide327

What’s My Design?

Clue 14

Ask each person about both exposure and disease at that point in time.

Cross Sectional Study

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide328

What’s My Design?

Clue 15

Ask both groups about their exposures in the past.

Case-Control Study

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide329

Flow Diagram

Random Assignment

Healthy People

Healthy People

-

What’s My Design?

Clue 16

Trial

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide330

What’s My Design?

Clue 17

Disease risk in exposed group is compared to disease risk in unexposed group.

Trial, Cohort Study, and Cross Sectional Study

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide331

DZ

Flow

Diagram

DZ

E

-

E

What’s My Design?

Clue 18

Cross Sectional Study

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide332

What’s My Design?

Clue 19

Select a healthy study sample.

Trial (?) and Cohort Study

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide333

What’s My Design?

Clue 20

Observe who has and has not been exposed.

Cohort and Cross-Sectional Studies

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide334

What’s My Design?

Clue 21

Give exposure to treatment group, but not control group.

Trial

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide335

Flow Diagram

Observational Study

E

Healthy People

Healthy People

E

-

What’s My Design?

Clue 22

Cohort Study

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide336

What’s My Design?

Clue 23

Epidemiologist is involved after disease has occurred and relies on subjects’ memories to gather information about exposure.

Case-Control Study

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide337

What’s My Design?

Clue 24

Select a study sample.

Trial, Cohort, Case-Control, and Cross Sectional Studies

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide338

DZ

Flow Diagram

Observational Study

E

DZ

Healthy People

Healthy People

DZ

E

-

DZ

What’s My Design?

Clue 25

Cohort Study

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide339

What’s My Design?

Clue 26

Epidemiologist gathers data only at that one point in time.

Cross Sectional Study

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide340

DZ

Flow Diagram

DZ

DZ

DZ

What’s My Design?

Clue 27

Trial and Cohort Study

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide341

What’s My Design?

Clue 28

Follow through time and compare risk of disease in exposed group to risk of disease in unexposed group.

Trial and Cohort Study

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide342

What’s My Design?

Clue 29

Epidemiologist is involved during the entire time from exposure to disease.

Trial and Cohort Study

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide343

DZ

Flow

Diagram

DZ

E

E

What’s My Design?

Clue 30

Cross Sectional Study

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide344

Flow

Diagram

DZ

-

DZ

What’s My Design?

Clue 31

Case-Control Study

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide345

Select a study sample.

Ask each person about both exposure and disease at that point in time.

Disease risk in exposed group is compared to disease risk in unexposed group.

Epidemiologist gathers data only at that one point in time.

What’s My Design?

Clue 32

Cross Sectional Study

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide346

Select a group of people with disease and a similar group of people without disease.

Ask both groups about their exposures in the past.

Compare percent of exposed people in the two groups.

Epidemiologist is involved after disease has occurred and relies on subjects’ memories to gather information about exposure.

What’s My Design?

Clue 33

Case-Control Study

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide347

Select a healthy study sample.

Observe who has and has not been exposed.

Follow through time and compare risk of disease in exposed group to risk of disease in unexposed group.

Epidemiologist is involved during the entire time from exposure to disease.

What’s My Design?

Clue 34

Cohort Study

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide348

Assign treatment and control groups.

Give exposure to treatment group, but not control group.

Follow through time and compare risk of disease in treatment group with risk of disease in control group.

Epidemiologist is involved during the entire time from exposure to disease.

What’s My Design?

Clue 35

Trial

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide349

What’s My Design?

End Epi Team Challenge

Detectives in the Classroom - Investigation 2-7: Epi Team Challenge

slide351

Which Design Is Best?

Which Design Is Best?

Detectives in the Classroom - Investigation 2-8: Which Design Is Best?

slide352

Epi Team Challenge

Study Designs

Main Strengths

Main Weaknesses

Trial

1

5

Cohort Study

6

2

Case-Control Study

3

7

Cross-Sectional Study

8

4

Epi Team Challenge

Detectives in the Classroom - Investigation 2-8: Which Design Is Best?

slide353

Epi Team Challenge

Study Designs

Main Strengths

Main Weaknesses

Trial

Case-

Control

Cohort

Cross-

Sectional

Controlled

Trial

1

5

Cohort Study

6

2

Case-Control Study

3

7

Cross-Sectional Study

8

4

Epi Team Challenge

Detectives in the Classroom - Investigation 2-8: Which Design Is Best?

slide354

Epi Team Challenge

Study Designs

Main Strengths

Main Weaknesses

Trial

1

5

Cohort Study

6

2

Case-Control Study

3

7

Cross-Sectional Study

8

4

Epi Team Challenge

Fastest

Which study design is the fastest?

Detectives in the Classroom - Investigation 2-8: Which Design Is Best?

slide355

Epi Team Challenge

Study Designs

Main Strengths

Main Weaknesses

Time Consuming

Trial

1

5

Cohort Study

Time Consuming

6

2

Case-Control Study

3

7

Cross-Sectional Study

8

4

Fastest

Which study designs are the most time consuming?

Detectives in the Classroom - Investigation 2-8: Which Design Is Best?

slide356

Epi Team Challenge

Study Designs

Main Strengths

Main Weaknesses

Trial

1

5

Cohort Study

6

2

Case-Control Study

3

7

Cross-Sectional Study

8

4

Most Scientifically Sound

Time Consuming

Time Consuming

Fastest

Which study design is the most scientifically sound?

Detectives in the Classroom - Investigation 2-8: Which Design Is Best?

slide357

Epi Team Challenge

Study Designs

Main Strengths

Main Weaknesses

Trial

1

5

Cohort Study

6

2

Case-Control Study

3

7

Cross-Sectional Study

8

4

Most Scientifically Sound

Time Consuming

Time Consuming

Can Study Rare Diseases

Fastest

Which study design is best for studying rare diseases?

Detectives in the Classroom - Investigation 2-8: Which Design Is Best?

slide358

Epi Team Challenge

Study Designs

Main Strengths

Main Weaknesses

Trial

1

5

Cohort Study

6

2

Case-Control Study

Possible Time-Order Confusion

3

7

Cross-Sectional Study

Possible Time-Order Confusion

8

4

Most Scientifically Sound

Time Consuming

Time Consuming

Can Study Rare Diseases

Fastest

Which study designs do not identify the time order of exposure and disease?

Detectives in the Classroom - Investigation 2-8: Which Design Is Best?

slide359

Epi Team Challenge

Study Designs

Main Strengths

Main Weaknesses

Trial

1

5

Cohort Study

6

2

Case-Control Study

3

7

Cross-Sectional Study

8

4

Time Consuming

Most Scientifically Sound

Time Consuming

Possible Time-Order Confusion

Can Study Rare Diseases

Possible Time-Order Confusion

Fastest

Least Confidence in Findings

Which study design gives the least confidence in findings?

Detectives in the Classroom - Investigation 2-8: Which Design Is Best?

slide360

Epi Team Challenge

Study Designs

Main Strengths

Main Weaknesses

Trial

1

5

Cohort Study

6

2

Case-Control Study

3

7

Cross-Sectional Study

8

4

Time Consuming

Most Scientifically Sound

Best Measure of Exposure

Time Consuming

Can Study Rare Diseases

Possible Time-Order Confusion

Possible Time-Order Confusion

Fastest

Least Confidence in Findings

Which study design provides the best measure of exposure?

Detectives in the Classroom - Investigation 2-8: Which Design Is Best?

slide361

Epi Team Challenge

Study Designs

Main Strengths

Main Weaknesses

Trial

1

5

Cohort Study

6

2

Case-Control Study

3

7

Cross-Sectional Study

8

4

Time Consuming

Most Scientifically Sound

Best Measure of Exposure

Most Accurate Observational Study

Time Consuming

Possible Time-Order Confusion

Can Study Rare Diseases

Possible Time-Order Confusion

Fastest

Least Confidence in Findings

Which study design is the most accurate observational study?

Detectives in the Classroom - Investigation 2-8: Which Design Is Best?

slide362

Epi Team Challenge

Study Designs

Main Strengths

Main Weaknesses

Trial

1

5

Cohort Study

6

2

Case-Control Study

3

7

Cross-Sectional Study

8

4

Time Consuming

Most Scientifically Sound

Best Measure of Exposure

Most Accurate Observational Study

Time Consuming

Possible Time-Order Confusion

Can Study Rare Diseases

Possible Time-Order Confusion

Fastest

Least Confidence in Findings

Least Expensive

Which study design is the least expensive?

Detectives in the Classroom - Investigation 2-8: Which Design Is Best?

slide363

Epi Team Challenge

Study Designs

Main Strengths

Main Weaknesses

Trial

1

5

Cohort Study

6

2

Case-Control Study

3

7

Cross-Sectional Study

8

4

Time Consuming

Most Scientifically Sound

Unethical for Harmful Exposures

Best Measure of Exposure

Time Consuming

Most Accurate Observational Study

Possible Time-Order Confusion

Can Study Rare Diseases

Fastest

Possible Time-Order Confusion

Least Confidence in Findings

Least Expensive

Which study design would be unethical for harmful exposures?

Detectives in the Classroom - Investigation 2-8: Which Design Is Best?

slide364

Epi Team Challenge

Study Designs

Main Strengths

Main Weaknesses

Trial

1

5

Cohort Study

6

2

Case-Control Study

3

7

Cross-Sectional Study

8

4

Time Consuming

Most Scientifically Sound

Unethical for Harmful exposures

Best Measure of Exposure

Time Consuming

Most Accurate Observational Study

Good Measure of Exposure

Possible Time-Order Confusion

Can Study Rare Diseases

Fastest

Possible Time-Order Confusion

Least Confidence in Findings

Least Expensive

Which study design provides a good measure of exposure?

Detectives in the Classroom - Investigation 2-8: Which Design Is Best?

slide365

Epi Team Challenge

Study Designs

Main Strengths

Main Weaknesses

Trial

1

5

Most Expensive

Cohort Study

Most Expensive

6

2

Case-Control Study

3

7

Cross-Sectional Study

8

4

Most Scientifically Sound

Time Consuming

Unethical for Harmful exposures

Best Measure of Exposure

Time Consuming

Most Accurate Observational Study

Good Measure of Exposure

Possible Time-Order Confusion

Can Study Rare Diseases

Fastest

Possible Time-Order Confusion

Least Expensive

Least Confidence in Findings

Which study designs are the most expensive?

Detectives in the Classroom - Investigation 2-8: Which Design Is Best?

slide366

Epi Team Challenge

Study Designs

Main Strengths

Main Weaknesses

Trial

1

5

Most Expensive

Cohort Study

Most Expensive

6

2

Case-Control Study

3

7

Cross-Sectional Study

8

4

Most Scientifically Sound

Time Consuming

Unethical for Harmful exposures

Best Measure of Exposure

Time Consuming

Most Accurate Observational Study

Good Measure of Exposure

Can Study Rare Diseases

Possible Time-Order Confusion

Relatively Less Expensive and Relatively Fast

Possible Time-Order Confusion

Fastest

Least Confidence in Findings

Least Expensive

Which study design is relatively less expensive and relatively fast?

Detectives in the Classroom - Investigation 2-8: Which Design Is Best?

slide367

Epi Team Challenge

Study Designs

Main Strengths

Main Weaknesses

Trial

1

5

Most Expensive

Cohort Study

Most Expensive

6

2

Case-Control Study

3

7

Cross-Sectional Study

8

4

Time Consuming

Most Scientifically Sound

Unethical for Harmful exposures

Best Measure of Exposure

Time Consuming

Most Accurate Observational Study

Good Measure of Exposure

Can Study Rare Diseases

Possible Time-Order Confusion

Possible Error in Recalling Past Exposures

Relatively Less Expensive and Relatively Fast

Possible Time-Order Confusion

Fastest

Least Confidence in Findings

Least Expensive

Which study design creates thepossibility of error in recalling past exposures?

Detectives in the Classroom - Investigation 2-8: Which Design Is Best?

slide368

Study Designs

Main Strengths

Main Weaknesses

Trial

1

5

Most Expensive

Cohort Study

Most Expensive

6

2

Case-Control Study

3

7

Cross-Sectional Study

8

4

Which Design Is Best?

Time Consuming

Most Scientifically Sound

Unethical for Harmful exposures

Best Measure of Exposure

Time Consuming

Most Accurate Observational Study

Good Measure of Exposure

It depends ….

Possible Time-Order Confusion

Can Study Rare Diseases

Relatively Less Expensive and Relatively Fast

Possible Error in Recalling Exposures

Fastest

Possible Time-Order Confusion

Least Expensive

Least Confidence in Findings

Which Design Is Best?

Detectives in the Classroom - Investigation 2-8: Which Design Is Best?

slide369

It depends on ….

  • Regulations
  • Time urgency
  • How much is known about the association
  • Money
  • Whether the exposure is believed to be beneficial

Detectives in the Classroom - Investigation 2-8: Which Design Is Best?

slide371

DZ

“fit”

2x2 Table

Flow Diagram

DZ

DZ

DZ

E

Healthy People

b

a

E

c

d

DZ

-

E

Healthy People

DZ

E

Designs, Diagrams, and Tables

&

Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables

slide372

DZ

E

DZ

Random Assignment

Healthy People

Healthy People

DZ

E

DZ

Controlled Trial

Where do these people “fit” in the 2x2 table?

DZ

DZ

E

a

E

2x2 Table

Flow Diagram

Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables

slide373

DZ

E

DZ

Random Assignment

Healthy People

Healthy People

DZ

E

DZ

Controlled Trial

Where do these people “fit” in the 2x2 table?

DZ

DZ

E

b

E

2x2 Table

Flow Diagram

Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables

slide374

DZ

E

DZ

Random Assignment

Healthy People

Healthy People

DZ

E

DZ

Controlled Trial

Where do these people “fit” in the 2x2 table?

DZ

DZ

E

E

c

2x2 Table

Flow Diagram

Flow Diagram

Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables

slide375

DZ

E

DZ

Random Assignment

Healthy People

Healthy People

DZ

E

DZ

Flow Diagram

Controlled Trial

Where do these people “fit” in the 2x2 table?

DZ

DZ

E

E

d

2x2 Table

Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables

slide376

DZ

E

DZ

DZ

E

DZ

Cohort Study

Where are these people in the flow diagram?

DZ

DZ

E

Healthy People

Healthy People

E

c

2x2 Table

Flow Diagram

Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables

slide377

DZ

E

DZ

DZ

E

DZ

Cohort Study

Where are these people in the flow diagram?

DZ

DZ

E

Healthy People

Healthy People

a

E

2x2 Table

Flow Diagram

Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables

slide378

DZ

E

DZ

DZ

E

DZ

Cohort Study

Where are these people in the flow diagram?

DZ

DZ

E

Healthy People

Healthy People

E

d

2x2 Table

Flow Diagram

Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables

slide379

DZ

E

DZ

DZ

E

DZ

Cohort Study

Where are these people in the flow diagram?

DZ

DZ

E

Healthy People

Healthy People

b

E

2x2 Table

Flow Diagram

Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables

slide380

E

DZ

E

E

DZ

E

Case-Control Study

Where do these people go in the 2x2 table?

DZ

DZ

E

a

E

Flow Diagram

2x2 Table

Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables

slide381

E

DZ

E

E

DZ

E

Case-Control Study

Where do these people go in the 2x2 table?

DZ

DZ

E

E

c

Flow Diagram

2x2 Table

Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables

slide382

E

DZ

E

E

DZ

E

Case-Control Study

Where do these people go in the 2x2 table?

DZ

DZ

E

b

E

Flow Diagram

2x2 Table

Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables

slide383

E

DZ

E

E

DZ

E

Case-Control Study

Where do these people go in the 2x2 table?

DZ

DZ

E

E

d

Flow Diagram

2x2 Table

Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables

slide384

DZ

DZ

E

E

Cross-Sectional Study

Where do these people go in the 2x2 table?

DZ

DZ

Flow Diagram

E

a

E

2x2 Table

Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables

slide385

DZ

DZ

E

E

Cross-Sectional Study

Where do these people go in the 2x2 table?

DZ

DZ

Flow Diagram

E

E

c

2x2 Table

Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables

slide386

DZ

DZ

E

E

Cross-Sectional Study

Where do these people go in the 2x2 table?

DZ

DZ

Flow Diagram

E

E

d

2x2 Table

Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables

slide387

DZ

DZ

E

E

Cross-Sectional Study

Where do these people go in the 2x2 table?

DZ

DZ

Flow Diagram

E

b

E

2x2 Table

Detectives in the Classroom – Investigation 2-9: Designs, Diagrams, and Tables

slide388

Enduring Epidemiological Understandings

Knowledge that “… is connected and organized, and … ‘conditionalized’ to specify the context in which it is applicable.”

National Research Council , Learning and Understanding

Teach Epidemiology

slide389

Making Group Comparisons and Identifying Associations

The goal of every epidemiological study is to harvest valid and precise information about the relationship between an exposure and a disease in a population.

The various study designs merely represent different ways of harvesting this information.

Essentials in Epidemiology in Public Health

Ann Aschengrau and George R. Seage III

Teach Epidemiology

slide390

Time Check

1:15 PM

slide392

Teach Epidemiology

Teach Epidemiology

slide395

Epidemiology is …

… the study of the distribution and determinants of health-related states or events in specified populations and the application of this study to the control of health problems.

Leon Gordis, Epidemiology, 2000

slide396

Epidemiology is …

… the study of how and why diseases are distributed in the population the way they are … in other words, the study of why some get sick and some don’t.

Donald F. Austin and S. Benson Werner, Epidemiology for the Health Sciences, 1974

slide398

The New York Times

ON THE WEB

March 29, 2002

A Study Finds More Links Between TV and Violence

By GINA KOLATA

“… the study of the distribution and determinants of health-related states or events …”

1

slide399

Study Designs

Experimental Studies

Randomized Controlled TrialsOther Experimental Studies

Observational Studies

Cohort StudiesCase-Control StudiesCross-Sectional StudiesEcologic Studies

Cohort Studies

slide400

Cohort Study

  • A study in which a group of people is followed over time
  • The group is made up of people who have the exposure of interest and people who do not have the exposure of interest
  • Exposed and unexposed people are followed over time to determine whether they experience the outcome
slide401

Cohort

Latin: Warriors, 1/10 of a Legion

Epidemiologist: A designated group of persons who are followed or traced over a period of time

slide402

Cohort

Latin: Warriors, 1/10 of a Legion

Epidemiologist: A designated group of persons who are followed or traced over a period of time

slide403

Exposure - Outcome

When epidemiologists ask a question, it is often of the form:

Does ______________ cause ______________?

(exposure)

(outcome)

slide404

Exposure

Refers to a factor we think may cause the outcome that we are studying

Could be an environmental agent, a personal characteristic, or a behavioral factor

slide405

Outcome

Refers to a factor that we think may be a consequence of the exposure that we are studying

Could be any kind of medical or social problem

slide406

Exposure - Outcome

When epidemiologists ask a question, it is often of the form:

Does ______________ cause ______________?

(exposure)

(outcome)

slide407

Exposure - Outcome

When epidemiologists ask a question, it is often of the form:

Does ______________ cause ______________?

(exposure)

(outcome)

For example:

Do diesel exhaust fumes from school buses cause asthma?

Does eating chocolate cause acne?

Are males at higher risk of automobile accidents?

Does immunization with the measles vaccine prevent measles?

Does acupuncture result in pain relief?

slide408

Exposure - Outcome

Outcome

Exposure

Diesel exhaust

Eating chocolate

Male gender

Measles immunization

Acupuncture

Asthma

Acne

Automobile accidents

Measles

Pain relief

slide409

Outcome

Exposed

No Outcome

March 29, 2002

A Study Finds More Links Between TV and Violence

Outcome

By GINA KOLATA

Not Exposed

-

No Outcome

2

Cohort Study Flow Diagram

Cohort

Time

A designated group of persons who are followed or traced over a period of time

slide410

Aggressive Acts

Watching TV for > 1 hrs per day

No Aggressive Acts

March 29, 2002

A Study Finds More Links Between TV and Violence

Aggressive Acts

Watching TV for < 1 hr per day

By GINA KOLATA

-

No Aggressive Acts

2

Cohort Study Flow Diagram

Adolescents & Young Adults

At age 14

By age 22

A designated group of persons who are followed or traced over a period of time

slide411

Lord Kelvin

When you can measure what you are speaking about, and express it in numbers, you know something about it.

But when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meager and unsatisfactory kind.

slide412

By age 22

Express it in Numbers

At age 14

Watched TV > 1 hour per day

154 reported aggressive acts

465 did not report aggressive acts

slide413

By age 22

No Outcome

Outcome

Total

Exposed

3

Express it in Numbers

At age 14

Watched TV > 1 hour per day

154 reported aggressive acts

465 did not report aggressive acts

slide414

By age 22

3

Express it in Numbers

At age 14

Watched TV > 1 hour per day

154 reported aggressive acts

465 did not report aggressive acts

No Aggressive Acts

Aggressive Acts

No Outcome

Outcome

Total

Total

Watched TV > 1 hour per day

Exposed

154

465

619

slide415

Risk

The probability that an event will occur, for example, that an individual will become ill or die, within a period of time

slide416

=

24.9%

4

Risk

154

154

=

(154 + 465)

619

No Aggressive Acts

Aggressive Acts

No Outcome

Outcome

Total

Total

Watched TV > 1 hour per day

Exposed

154

465

619

slide417

Hypothesis

An educated guess

An unproven idea, based on observation or reasoning, that can be proven or disproven through investigation

Watching TV causes aggressive acts.

slide418

Does watching TV cause aggressive acts?

154

154

=

=

24.9%

(154 + 465)

619

No Aggressive Acts

Aggressive Acts

No Outcome

Outcome

Total

Risk

Total

Watched TV > 1 hour per day

Exposed

154

465

619

24.9%

slide419

Aggressive Acts

No Aggressive Acts

Aggressive Acts

-

No Aggressive Acts

Does watching TV cause aggressive acts?

24.9% risk of committing an aggressive act

Watching TV for > 1 hrs per day

Adolescents & Young Adults

? risk of committing an aggressive act

Watching TV for < 1 hr per day

At 14 years

By 22 years

slide420

Aggressive Acts

No Aggressive Acts

Aggressive Acts

-

No Aggressive Acts

Does watching TV cause aggressive acts?

24.9% risk of committing an aggressive act

Watching TV for > 1 hrs per day

Adolescents & Young Adults

? risk of committing an aggressive act

Watching TV for < 1 hr per day

Comparison Group

At 14 years

By 22 years

slide421

At age 14

By age 22

Watched TV < 1 hour per day

Watched TV < 1 hour per day

5

Comparison Group

5 reported aggressive acts

83 did not report aggressive acts

No Aggressive Acts

Aggressive Acts

No Outcome

Outcome

Total

Risk

Total

Watched TV > 1 hour per day

Exposed

154

465

619

24.9%

slide422

Watched TV < 1 hour per day

Comparison Group

At age 14

By age 22

Watched TV < 1 hour per day

5 reported aggressive acts

83 did not report aggressive acts

No Aggressive Acts

Aggressive Acts

Outcome

Total

Risk

Total

Watched TV > 1 hour per day

Exposed

154

465

619

24.9%

5

83

88

5.7%

slide423

Contingency Table

A cross-classification of data where categories of one variable are presented in rows and categories of another variable presented in columns.

slide424

Outcome

Exposure

Watched TV < 1 hour per day

Contingency Table

No Aggressive Acts

Aggressive Acts

No Outcome

Outcome

Total

Risk

Total

Watched TV > 1 hour per day

Exposed

154

465

619

24.9%

5

83

88

5.7%

slide425

Watched TV < 1 hour per day

Does watching TV cause aggressive acts?

No Aggressive Acts

Aggressive Acts

No Outcome

Outcome

Total

Risk

Total

Watched TV > 1 hour per day

Exposed

154

465

619

24.9%

5

83

88

5.7%

slide426

Times as Likely

Watched TV < 1 hour per day

6

Does watching TV cause aggressive acts?

No Aggressive Acts

Aggressive Acts

No Outcome

Outcome

Total

Risk

Total

Watched TV > 1 hour per day

Exposed

154

465

619

24.9%

4.4

5

83

88

5.7%

Compared to those who watched TV for < 1 hour per day, those who watched TV for > 1 hours per day were ____ times as likely to commit aggressive acts.

slide427

Risk

The probability that an event will occur, for example, that an individual will become ill or die, within a specified period of time

Cartoon from Larry Gotnick’s The Cartoon Guide to Statistics, HarperPerennial, 1993

slide428

Relative Risk

A way of quantifying the relationship between two risks

Tells us the number of times

one risk is larger or smaller than another

Cartoon from Larry Gotnick’s The Cartoon Guide to Statistics, HarperPerennial, 1993

slide430

Epidemiology is ….

… the study of the distribution and determinants of health-related states or events in specified populations and the application of this study to the control of health problems.

… the study of the distribution and determinants of health-related states or events in specified populations and the application of this study to the control of health problems.

Leon Gordis, Epidemiology, 2000

slide431

Watched TV < 1 hour per day

“… the control of health problems”

What should be done?

No Aggressive Acts

Relative Risk

Aggressive Acts

No Outcome

Outcome

Total

Risk

Total

Watched TV > 1 hour per day

Exposed

154

465

619

24.9%

4.4

5

83

88

5.7%

slide432

Association

When things turn up together

slide433

No Eggs

Relative Risk

Eggs

Total

Risk

154

465

619

24.9%

Ham

4.4

No Ham

5

83

88

5.7%

Association

When things turn up together

slide434

Relative Risk

No Thunder

Thunder

Total

Risk

Light-ning

154

465

619

24.9%

4.4

No Light-ning

5

83

88

5.7%

Association

When things turn up together

slide435

Relative Risk

Ball on Red

No Ball on Red

Total

Risk

Bet on Red

154

465

619

24.9%

4.4

No Bet on Red

5

83

88

5.7%

Association

When things turn up together

slide436

Relative Risk

Auto Accident

No Auto Accident

Total

Risk

Ate Pretzels

154

465

619

24.9%

4.4

Did Not Eat Pretzels

5

83

88

5.7%

Association

When things turn up together

slide437

Association

Cause

Auto Accidents

Pretzels

Association

Drinking Alcoholic Beverages

Another Exposure

Association of Interest

slide438

Auto Accidents

Pretzels

Confounding

Drinking Alcoholic Beverages

Another Exposure

Association

Cause

Association of Interest

When an observed association between an exposure and an outcome is distorted because the exposure of interest is associated with some other exposure that causes the outcome

slide439

Confounding

  • Confounding is the distortion of an exposure-outcome association brought about by the association of another factor with both outcome and exposure.
  • A confounder confuses our conclusions about the relationship between an exposure and an outcome.
slide440

Auto Accidents

Pretzels

“… the control of health problems”

X

Drinking Alcoholic Beverages

Another Exposure

Association

Cause

X

Association of Interest

slide441

No Aggressive Acts

Relative Risk

Aggressive Acts

Total

Risk

Total

Watched TV > 1 hour per day

154

465

619

24.9%

4.4

Watched TV < 1 hour per day

5

83

88

5.7%

Association

When things turn up together

slide442

?

Association

Cause

Confounding

Aggressive Acts

Watching TV

Association of Interest

When an observed association between an exposure and an outcome is distorted because the exposure of interest is associated with some other exposure that causes the outcome

slide443

Association

Cause

Confounding

Living in a Violent Neighborhood

Aggressive Acts

Watching TV

Association of Interest

When an observed association between an exposure and an outcome is distorted because the exposure of interest is associated with some other exposure that causes the outcome

slide444

Association

Cause

Confounding

Lack of Adequate Supervision

Aggressive Acts

Watching TV

Association of Interest

When an observed association between an exposure and an outcome is distorted because the exposure of interest is associated with some other exposure that causes the outcome

slide445

Association

Cause

“… the control of health problems”

X

Lack of Adequate Supervision

X

Aggressive Acts

Watching TV

Association of Interest

When an observed association between an exposure and an outcome is distorted because the exposure of interest is associated with some other exposure that causes the outcome

slide446

Control of Confounding

  • At Design Stage:
    • Randomization
    • Matching
    • Restricting study to certain groups
  • At Analysis Stage:
    • Quantitative methods
      • Stratification
      • Standardization
      • Regression
slide447

The New York Times

ON THE WEB

March 29, 2002

A Study Finds More Links Between TV and Violence

By GINA KOLATA

Recap

“… the study of the distribution and determinants of health-related states or events …”

slide448

Outcome

Exposed

No Outcome

March 29, 2002

A Study Finds More Links Between TV and Violence

Cohort

Outcome

By GINA KOLATA

Not Exposed

-

No Outcome

Time

Recap

Study Design

A designated group of persons who are followed or traced over a period of time

slide449

Recap

Risk

154

154

=

=

24.9%

(154 + 465)

619

No Aggressive Acts

Aggressive Acts

No Outcome

Outcome

Total

Risk

Total

Watched TV > 1 hour per day

Exposed

154

465

619

24.9%

slide450

Outcome

Exposure

Watched TV < 1 hour per day

Recap

Contingency Table

No Aggressive Acts

Aggressive Acts

No Outcome

Outcome

Total

Risk

Total

Watched TV > 1 hour per day

Exposed

154

465

619

24.9%

5

83

88

5.7%

slide451

Watched TV < 1 hour per day

Recap

Relative Risk

No Aggressive Acts

Aggressive Acts

No Outcome

Relative Risk

Outcome

Total

Risk

Total

Watched TV > 1 hour per day

Exposed

154

465

619

24.9%

4.4

5

83

88

5.7%

slide452

Auto Accident

No Auto Accident

Ate Pretzels

Did Not Eat Pretzels

Recap

Association

Relative Risk

Total

Risk

154

465

619

24.9%

4.4

5

83

88

5.7%

slide453

Association

Cause

Recap

Confounding

?

Aggressive Acts

Watching TV

Association of Interest

When an observed association between an exposure and an outcome is distorted because the exposure of interest is associated with some other exposure that causes the outcome

slide454

Association

Cause

Recap

“… the control of health problems”

X

?

X

Aggressive Acts

Watching TV

Association of Interest

When an observed association between an exposure and an outcome is distorted because the exposure of interest is associated with some other exposure that causes the outcome

slide455

The New York Times

ON THE WEB

March 29, 2002

A Study Finds More Links Between TV and Violence

By GINA KOLATA

“… the study of the distribution and determinants of health-related states or events …”

7

slide456

The New York Times

ON THE WEB

March 29, 2002

A Study Finds More Links Between TV and Violence

By GINA KOLATA

“… the study of the distribution and determinants of health-related states or events …”

8

slide457

9

Assessment

In a study of the hypothesis that drinking orange juice prevents the flu, 3,000 students at Wright High School, who did not have the flu on December 31, 2000, were followed from January 1 through March 31, 2001. By the end of the study, among the 1000 students who drank orange juice, 123 students had developed the flu. Among the 2000 students who did not drink orange juice, 342 students had developed the flu. Display the above data on a 2x2 table, calculate risks of flu, calculate the relative risk, and explain whether or not the results support the hypothesis that drinking orange juice prevents the flu.

slide459

Teach Epidemiology

Teach Epidemiology

slide461

Time Check

2:45 PM

slide463

Teach Epidemiology

Teach Epidemiology

slide464

Time Check

3:00 PM

slide466

Teach Epidemiology

Teach Epidemiology

slide467

Tours

Teach Epidemiology

slide468

Tours

Broadcast Studios

Teach Epidemiology

slide469

Tours

Emergency Operation Center

Teach Epidemiology

slide470

Time Check

4:00 PM