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Summer Course: Introduction to Epidemiology. August 25 , 0900-1030. C ourse overview; Epidemiology background. Dr. N. Birkett, Department of Epidemiology & Community Medicine, University of Ottawa. A Disaster. 2,224 people One week later: 1,513 are dead (68%) Very high mortality:

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c ourse overview epidemiology background

Summer Course:Introduction to Epidemiology

August 25, 0900-1030

Course overview; Epidemiology background

Dr. N. Birkett,

Department of Epidemiology & Community Medicine,

University of Ottawa

a disaster
A Disaster
  • 2,224 people
  • One week later:
    • 1,513 are dead (68%)
  • Very high mortality:
    • World Trade Centre (9/11):
      • 2,800 died but 10,000 were ‘at risk’
      • 28%
    • Malaria:
      • 25% lifetime mortality
    • Plane crashes:
      • about 33% die
resolution
Resolution
  • Sinking of the Titanic
  • Patterns of mortality, not just the high mortality rate
  • Reflects cultural norms and values of the time
    • Women and children first
    • Upper classes had better access to lifeboats, etc.
course overview 1
Course Overview (1)
  • Lectures:
    • 0900-1030 (0845-1015 T/R)
    • 1100-1230 (1045-1215 T/R)
    • 1330-1500
    • 1530-1700 (Friday: informal Q&A)
  • Tuesday/Thursday lunch videos
    • Pizza lunch provided. Sign-up!
  • Nutrition/networking breaks (provided):
    • 1030-1100 (1015-1045 T/R).
    • 1500-1530
  • No exam or formal evaluation
course overview 2
Course Overview (2)
  • Main course textbook:
    • Medical Epidemiology. RS Greenberg et al. Lange Medical Books.
    • Copies of this book have been provided to you in your registration package.
      • A small selection of other Epidemiology books is available at the Ottawa University Bookstore, located in the main lobby of the Ottawa Hospital, General campus.
  • Lunch is not provided on Monday, Wednesday or Friday
    • can be purchased at local cafes at the Ottawa Hospital or CHEO.
course overview 3
Course Overview (3)
  • Lunch-time videos (1215-1315):
    • Includes a pizza lunch
      • Sign-up for type of pizza and drink which you would like.
    • Tuesday: Esophageal Cancer in China (Nova)
    • Thursday: Typhoid Mary.(Nova).
course overview 4
Course Overview (4)
  • Friday afternoon (1500-when we get tired)
      • General Q&A opportunity
      • Two faculty members
      • You can ask anything you want (but, try and stay relate to course and the field )
      • Chance to explore problem areas, future plans and so on.
course overview 5
Course Overview (5)
  • Acquire a general appreciation of the historical development of the discipline of epidemiology
  • Comprehend the basic concepts of epidemiology
  • Main topics:
    • Approaches to measuring health
    • The major epidemiological study designs
    • Sources of biases in epidemiology and what to do about them
    • Infectious diseases and outbreak investigation
    • Awareness of application to fields of interest
stamp s law
Stamp’s Law

The Government is extremely fond of amassing great quantities of statistics. These are raised to the nth degree, the cube roots are extracted, and the results are arranged into elaborate and impressive displays. What must be kept ever in mind, however, is that in every case, the figures are first put down by a village watchman, and he puts down anything he damn well pleases!

Sir Josiah Stamp (1880-1941),

Her Majesty’s Collector of Internal Revenue.

scenario 2 1
Scenario #2 (1)

A 29-year-old previously healthy man was referred to the University of California at Los Angeles (UCLA) Medical Center with a history of fever, fatigue, lymph node enlargement and weight loss of almost 25 lb. over the preceding 8 months. He had a temperature of 39.5C, appeared physically wasted and had swollen lymph nodes. Laboratory evaluation revealed a depressed level of peripheral blood lymphocytes. The patient suffered from simultaneous infections involving Candida albicansin his upper digestive tract, cytomegalovirus in his urinary tract and Pnuemocystis carinii in his lungs. Although antibiotic therapy was administered, the patient remained severely ill.

scenario 2 2
Scenario #2 (2)
  • Very unusual infections
    • Mainly occur in people with immune system suppression
  • Highly unusual to have three different infections in three different organ systems.
  • Alert MD’s realized that there had been 4 other men with similar ‘odd’ diseases at UCLA in the past 6 months.
  • A report was prepared and submitted to MMWR (Morbidity and Mortality Weekly Report).
scenario 2 3
Scenario #2 (3)

On June 5, 1981, MMWR published a report of five cases of Pneumocystis carinii pneumonia (PCP) among previously healthy young men in Los Angeles. All of the men were described as “homosexuals”; two had died. Local clinicians and the Epidemic Intelligence Service Officer stationed at the Los Angeles County Department of Public Health, prepared the report and submitted it for MMWR publication in early May 1981. Before publication, MMWR editorial staff sent the submission to CDC experts in parasitic and sexually transmitted diseases. The editorial note that accompanied the published report stated that the case histories suggested a “cellular-immune dysfunction related to a common exposure” and a “disease acquired through sexual contact.”.

scenario 2 4
Scenario #2 (4)
  • What does this mean?
    • Local to Los Angeles
      • Medical curiosity
    • In other communities
      • Wider implications
      • Spread between communities?
      • Common source?
  • Report to public health authorities
  • “The report prompted additional case reports from New York City, San Francisco, and other cities.”
  • “At about the same time, CDC’s investigational drug unit, the sole distributor of pentamidine, the therapy for PCP, began to receive requests for the drug from physicians also to treat young men.”
scenario 2 5 a name was needed
Scenario #2 (5): A name was needed!

Originally was called

“gay-related immune deficiency”

“GRID”

Now: AIDS

scenario 2 6 a case definition
Scenario #2 (6): A case definition

CDC defines a case of AIDS as a disease, at least moderately predictive of a defect in cell-mediated immunity, occurring in a person with no known cause for diminished resistance to that disease. Such diseases include KS, PCP, and serious opportunistic infection(s). Diagnoses are considered to fit the case definition only if based on sufficiently reliable methods (generally histology or culture). However, this case definition may not include the full spectrum of AIDS manifestations, which may range from absence of symptoms (despite laboratory evidence of immune deficiency) to non-specific symptoms (e.g., fever, weight loss, generalized, persistent lymphadenopathy) to specific diseases that are insufficiently predictive of cellular immunodeficiency to be included in incidence monitoring (e.g., tuberculosis, oral candidiasis, herpes zoster) to malignant neoplasms that cause, as well as result from, immunodeficiency. Conversely, some patients who are considered AIDS cases on the basis of diseases only moderately predictive of cellular immunodeficiency may not actually be immunodeficient and may not be part of the current epidemic. Absence of a reliable, inexpensive, widely available test for AIDS, however, may make the working case definition the best currently available for incidence monitoring.

scenario 2 7
Scenario #2 (7)
  • Multiple case definitions since 1983
  • How wide spread is it? (Place)
  • Who gets the symptoms? (Who)
    • Look for common characteristics
      • Homosexual men, hemophiliacs and injection drug users.
      • What do they have in common?
        • Blood-to-blood contact
  • When do people get ill? (Time)
  • Is the disease becoming more (or less) commons? (Time)
definition of epidemiology
DEFINITION OF EPIDEMIOLOGY

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

anonymous definition
Anonymous definition 

Common sense made difficult

traditional epidemiology questions
Traditional Epidemiology Questions
  • Who gets disease ‘X’?
  • Why did someone get disease ‘X’?
  • What is going to happen to someone who has disease ‘X’?
  • What can we do to prevent someone getting disease ‘X’?
  • What can we do to help someone with disease ‘X’?
  • Why are more (or fewer) people getting disease ‘X’ now than before?
  • Why do people living in ‘Y’ get more (or less) of disease ‘X’ than people living in ‘Z’?
modern epidemiology questions
‘Modern’ Epidemiology Questions
  • How can we help someone be healthier?
  • Why did this person get ill while that person didn’t when they both smoked, etc.?
  • What is the role of government policies on health?
  • What is the role of research in directing policy?
  • How can we improve the health care system?
  • When is a community ‘healthy’?
  • How can we empower people to make informed decisions about their health?
  • How do we make sense of conflicting research results?
types of epidemiology
‘Types’ of Epidemiology

Clinical Epidemiology

Public Health Epidemiology

Nutritional Epidemiology

Genetic Epidemiology

Injury Epidemiology

Environmental Epidemiology

Social Epidemiology

Molecular Epidemiology

Psychiatric Epidemiology

Population Health

Epidemiology as

social action vs. science

definitions of health
Definitions of Health
  • A state of complete physical, mental and social well-being and not merely the absence of disease or infirmity. [The WHO, 1948]
  • A joyful attitude toward life and a cheerful acceptance of the responsibility that life puts upon the individual [Sigerist, 1941]
  • The ability to identify and to realize aspirations, to satisfy needs, and to change or cope with the environment. Health is therefore a resource for everyday life, not the objective of living. Health is a positive concept emphasizing social and personal resources, as well as physical capacities. (WHO Europe, 1986]
slide27

The healthiest people is not that which possesses the best or the greatest number of hospitals, but rather that which needs the fewest.

Chief ‘gesundheitfuhren’, Germany around 1935

some key dates in epidemiology
Some Key Dates in Epidemiology
  • 400BC Hippocrates
  • 1660’s John Graunt (birth of vital statistics)
  • 1660’s Thomas Sydenham (Classification of fevers)
  • 1753 James Lind (Studies on Scurvy)
  • 1774 Jenner and Jesty (smallpox immunization)
  • 1830’s James Farr (concept of rates, population health)
  • 1840’s Semmelweis (childbirth infections)
  • 1850’s John Snow (studies on cholera)
  • 1880’s Germ theory of Disease
  • 1900’s Mosquitoes and malaria
  • 1950’s Smoking and health
  • 1930-70 Tuskegee Syphilis study
hippocrates 400bc
Hippocrates (400BC)
  • Died at age 97!
  • Proposed a theory of medicine based on humours.
    • Remained the basis for medical thought for about 2,000 years
  • He was first epidemiologist and developed insights into public health. Was concerned with finding causes in order to prevent disease.
  • Emphasized need for clear observation
hippocrates 400bc 2
Hippocrates (400BC) [2]
  • Published three books on epidemiology.
  • Discussed the need to consider place, time, season, environmental circumstances
  • Role of water, diet, physical activity
  • Doctors need to know what diseases are common in their local area in order to treat patients.
some key dates in epidemiology1
Some Key Dates in Epidemiology
  • 400BC Hippocrates
  • 1660’s John Graunt (birth of vital statistics)
  • 1660’s Thomas Sydenham (Classification of fevers)
  • 1753 James Lind (Studies on Scurvy)
  • 1774 Jenner and Jesty (smallpox immunization)
  • 1830’s James Farr (concept of rates, population health)
  • 1840’s Semmelweis (childbirth infections)
  • 1850’s John Snow (studies on cholera)
  • 1880’s Germ theory of Disease
  • 1900’s Mosquitoes and malaria
  • 1950’s Smoking and health
  • 1930-70 Tuskegee Syphilis study
john graunt 1662
John Graunt (1662)

Performed early work on vital statistics registration.

‘When anyone dies, then, either by tolling or ringing a bell, or by bespeaking of a Grave of the Sexton, the same is known to the Searchers, corresponding to the said Sexton. The Searchers hereupon (who are ancient matrons, sworn to their office) repair to the place where the dead corpse lies, and by view of the same, and by other enquiries, they examine by what disease or causality the corpse did die.’

graunt 2
Graunt (2)

‘Hereupon they make their Report to the Parish-Clerk and he, every Tuesday night, carries in an Account of all the Burials and Christenings happening that Week, to the Clerk of the Hall. On Wednesday the general account is made up and printed and on Thursdays published and dispersed to the several Families, who pay four shillings per Annum for them.’

graunt 3
Graunt (3)
  • 75% mortality by age 25
  • Estimated errors in data (20% under-count)
  • Men have higher mortality rate than women
  • Most ‘greatly feared’ causes of death (e.g. starvation, leprosy) were uncommon.
  • Common causes of death:
    • old age,
    • consumption,
    • smallpox,
    • plague,
    • diseases of teeth,
    • Worms
  • Autumn is ‘most unhealthy season’
  • Distinguished between epidemic and endemic diseases.
some key dates in epidemiology2
Some Key Dates in Epidemiology
  • 400BC Hippocrates
  • 1660’s John Graunt (birth of vital statistics)
  • 1660’s Thomas Sydenham (Classification of fevers)
  • 1753 James Lind (Studies on Scurvy)
  • 1774 Jenner and Jesty (smallpox immunization)
  • 1830’s James Farr (concept of rates, population health)
  • 1840’s Semmelweis (childbirth infections)
  • 1850’s John Snow (studies on cholera)
  • 1880’s Germ theory of Disease
  • 1900’s Mosquitoes and malaria
  • 1950’s Smoking and health
  • 1930-70 Tuskegee Syphilis study
james farr
James Farr
  • MD and mathematician
  • Conducted fundamental research on anesthesia
  • Oversaw the General Registry Office,1839-1880
  • Recognized need for denominators.
  • Developed the Standardized Mortality Ratio (SMR) to adjust for age differences.
  • Developed first disease classification system (precursor of ICD system)
farr 2
Farr (2)
  • Living in densely populated areas gives increased mortality.
  • Living at lower elevations was associated with higher cholera mortality than higher elevations
  • Mortality decreased following improvements to sanitation
  • Widowers had a higher marriage rate than bachelors
some key dates in epidemiology3
Some Key Dates in Epidemiology
  • 400BC Hippocrates
  • 1660’s John Graunt (birth of vital statistics)
  • 1660’s Thomas Sydenham (Classification of fevers)
  • 1753 James Lind (Studies on Scurvy)
  • 1774 Jenner and Jesty (smallpox immunization)
  • 1830’s James Farr (concept of rates, population health)
  • 1840’s Semmelweis (childbirth infections)
  • 1850’s John Snow (studies on cholera)
  • 1880’s Germ theory of Disease
  • 1900’s Mosquitoes and malaria
  • 1950’s Smoking and health
  • 1930-70 Tuskegee Syphilis study
slide39

Two priests, a Dominican and a Jesuit met for their regular Monday morning walk. They got into a discussion about whether it was a sin to smoke and pray at the same time. The Jesuit was sure that it wasn’t a sin while the Dominican was sure that it was. Unable to resolve it, they decided to ask their superiors.

slide40

The next week, they met again.

Dominican: What did your superior say?

Jesuit: He said that it definitely was not a sin.

Dominican: That’s strange because mine said that it was a sin.

Jesuit:What did you ask him?

Dominican: Whether it was a sin to smoke while praying.

Jesuit: I asked if it was a sin to pray while smoking.

examples 1 streptomycin tb
Examples (1): Streptomycin & TB
  • First modern RCT (1946). Designed by Sir Bradford Hill
  • Four key features:
    • Random allocation to 2 treatment groups
    • Clear eligibility criteria
    • Precise endpoints (death) and blinding of MD’s reading x-rays (treatment arm unknown)
    • Addressed ethical issues. Introduced concept that not doing RCT would be unethical
  • BUT, by 1946, mortality from TB had decreased by about 90% due to public health interventions
examples 2 smoking lung cancer
Examples(2):Smoking & lung cancer
  • Doll & Hill (1950)
  • Marked increase in lung cancer mortality post WW1
  • Unclear why:
    • Better diagnosis
    • Environmental cause.
  • Doll and Hill’s work moved Epi from infectious diseases to chronic diseases.
  • BUT, evidence suggests it was based on work done in Germany in the 1930’s.
examples 2 smoking lung cancer1
Examples(2):Smoking & lung cancer
  • Invented case-control design.
  • 709 cases and 709 controls.
    • Used personal interview to recall smoking and other behaviors.
    • 99.7% of male cases smoked;
    • 95.8% of male controls smoked
    • OR=16
  • British Doctor’s study
    • Cohort
    • 20 years of follow-up
examples 3 framingham study
Examples (3):Framingham study
  • ‘Prototypical cohort study’ (1947)
  • Recruited 5,000 men living in Framingham, MA
  • Followed up every two years for 50 years
    • Interview
    • Physical exams
    • Various lab tests
  • Study is now following the off-spring of original participants.
  • Shows power of long-term follow-up with physical measures.
summary
Summary
  • Epidemiology is the study of diseases and conditions in human populations
  • Many applications to clinical and public health
  • Has a long history with many positive successes
  • Direct applications to disease control and health care delivery
  • Applications to understanding scientific basis for diseases.