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Welcome to EP711

AR% = AR x 100 I e. AR% = AR x 100 I e. AR% = AR x 100 I e. AR% = AR x 100 I e. AR% = AR x 100 I e. AR% = AR x 100 I e. AR% = AR x 100 I e. AR% = AR x 100

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Welcome to EP711

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  1. AR% = AR x 100 Ie AR% = AR x 100 Ie AR% = AR x 100 Ie AR% = AR x 100 Ie AR% = AR x 100 Ie AR% = AR x 100 Ie AR% = AR x 100 Ie AR% = AR x 100 Ie AR% = AR x 100 Ie AR% = AR x 100 Ie AR% = AR x 100 Ie AR% = AR x 100 Ie AR% = AR x 100 Ie AR% = AR x 100 Ie S (O-E)2 E S (O-E)2 E S (O-E)2 E S (O-E)2 E S (O-E)2 E S (O-E)2 E S (O-E)2 E S (O-E)2 E S (O-E)2 E S (O-E)2 E S (O-E)2 E S (O-E)2 E S (O-E)2 E S (O-E)2 E Welcome to EP713 Welcome to EP711 RR = a/(a+b) c/(c+d) RR = a/(a+b) c/(c+d) RR = a/(a+b) c/(c+d) RR = a/(a+b) c/(c+d) RR = a/(a+b) c/(c+d) RR = a/(a+b) c/(c+d) RR = a/(a+b) c/(c+d) RR = a/(a+b) c/(c+d) RR = a/(a+b) c/(c+d) RR = a/(a+b) c/(c+d) Odds Ratio = a/c b/d Odds Ratio = a/c b/d Odds Ratio = a/c b/d Odds Ratio = a/c b/d Odds Ratio = a/c b/d Odds Ratio = a/c b/d Odds Ratio = a/c b/d Odds Ratio = a/c b/d Odds Ratio = a/c b/d Odds Ratio = a/c b/d Odds Ratio = a/c b/d Odds Ratio = a/c b/d Odds Ratio = a/c b/d Odds Ratio = a/c b/d AR = Ie-Io Ie AR = Ie-Io Ie AR = Ie-Io Ie AR = Ie-Io Ie AR = Ie-Io Ie AR = Ie-Io Ie AR = Ie-Io Ie AR = Ie-Io Ie Welcome to EP711 AR% = AR x 100 Ie AR% = AR x 100 Ie S (O-E)2 E S(O-E)2 E S (O-E)2 E S (O-E)2 E S(O-E)2 E S (O-E)2 E S(O-E)2 E S (O-E)2 E S(O-E)2 E Welcome to EP713 RR = a/(a+b) c/(c+d) RR = a/(a+b) c/(c+d) Odds Ratio = a/c b/d Odds Ratio = a/c b/d Prevalence= Incidence x Average Duration Prevalence= Incidence x Average Duration Prevalence= Incidence x Average Duration Prevalence= Incidence x Average Duration Prevalence= Incidence x Average Duration Prevalence= Incidence x Average Duration

  2. You aren’t here to memorize facts and equations in order to regurgitate them on an exam. You are here to learn how to think in a structured way that enables you to identify the determinants of health and disease. Just because you can do something with PowerPoint doesn’t mean that you should.

  3. The take-home message from the online module on the evolution of epidemiology?

  4. The Black Death Bruegel’s Triumph of Death c. 1556

  5. Cause of the Plague? • God’s punishment • Miasmas: unseen vapors from swamps & cesspits • Contact with lepers • Walking in the hot sun The Black Death of 1349 killed two thirds of Norway’s population.

  6. The Real Causes • High population density • Poor sanitation (garbage attracts rats) • Poor personal hygiene Bacteria Bacteria Fleas Fleas Sylvatic Cycle Urban Cycle Garbage Rodents Rats

  7. What Was Missing? • Inability to identify the determinants & to institute effective preventive measures was not due to a lack of technology. • Why they failed: • No concept of testing hypotheses in a systematic way in groups of people • No structured way of evaluating information. They had a hypothesis and they had data. They didn’t think in a structured, systematic way. They didn’t test the hypotheses. What factors are associated with disease? What treatments/preventions are most effective? You need to think in a structured way.

  8. You aren’t here to memorize facts. You are here to develop skills in critical thinking and problem solving. Problem: Large class stuck in L-110

  9. Laurentius de Voltolina, late 1300s

  10. Course Modifications • Online Modules • Pre-quizzes • Class • Post-quizzes (being reviewed) • EpiTools (Excel application) • Discussions • Exercises http://sph.bu.edu/otlt/lamorte/ep713/

  11. What & How to Study? • Learning objectives! • Read ahead. Jot down questions. • Come to class. Ask questions. Participate. • Do the ‘quizzes’ by yourself. Use them to identify areas of misunderstanding, then… • Ask the TAs or me for clarification if necessary. • Review for exams efficiently. Re-do problems; review shaky areas. Study definitions. • Keep up. • There should be abundant access to help. • Before and after class • Pretty much any mutually agreeable time. • Email • Phone

  12. EP713: Introduction to Epidemiology Instructor: Wayne W. LaMorte, M.D., Ph.D., M.P.H. Talbot 422 East Office phone: (617) 638-5073 wlamorte@bu.edu TAs:

  13. Do flu shots cause dystonia disorder?

  14. Descriptive Epidemiology

  15. 8:00 AM, Sept. 25 The cause? What should we do?

  16. ER in Lower Manhattan 10:25 AM another 11:10 AM three more 11:20 AM two more 11:40 AM two more 12:00 another 12:20 another All had become ill suddenly and were now blue and had varying degrees of abdominal cramps and diarrhea. An epidemic?

  17. Sodium nitrite, which had been used as a meat preservative, is a poison. Cooking usually destroys residual. What factors provided clues about the causes of disease?

  18. Descriptive Epidemiology Provides Clues • What factors might be associated with disease? • Are there similarities among the diseased? • Are there differences between diseased & well people? • What correlates with disease? • Person: characteristics? • Place: specific locations or settings? • Time: does it vary over time?

  19. Evolution of Medical Information 1. Description & hypothesis generation 2. Hypothesis testing to establish valid associations 3. Evaluation of efficacy of treatment or prevention

  20. Descriptive Epidemiology • Identify type & extent of diseases in population. Alert us to new health problems, trends in disease, unusual cases, high risk groups. • Who is getting disease? Their characteristics? (Describe: age, gender, race, geography, habits, diet, drugs used etc.) • How does disease vary across place & time? (trends) • They generate hypotheses for analytic studies. But, can’t establish validity of an association.

  21. Sources of Data • Death Certificates & Birth Certificates; Census • Disease Registries (cancer, ALS, MS) • Hospital Discharge Registry • Infectious Disease Reporting (MAVEN) • Commercial data (sales of tobacco, drugs, etc.) • Surveys

  22. Large Surveys • National Survey of Family Growth • National Health Interview Survey (NHIS) • National Health & Nutrition Examination Survey (NHANES) • Behavioral Risk Factor Surveillance System (BFRSS) • National Health Care Survey • National Notifiable Disease Surveillance System • Surveillance of AIDS and HIV Infection • National Immunization Survey • Survey of Occupational Injuries and Illnesses • National Survey on Drug Use and Health

  23. Hypotheses arise from observation of … • Differences: If the frequency of disease differs in two circumstances, it may be due to a factor that differs in the two circumstances. Example: stomach cancer in Japan & US • Similarities: If a high frequency of disease is found in several different circumstances & one can identify a common factor, then the common factor may be responsible. Example: AIDS in IV drug users, or recipients of transfusions, & hemophiliacs. • Correlations: If the frequency of disease varies in relation to some factor, then that factor may be a cause of the disease. Example: differences in colon cancer vary with per capita meat consumption.

  24. Disease Outbreaks: How do you know if there is a problem?

  25. Surveillance Reportable diseases

  26. Pandemic: Worldwide epidemics # cases of a disease Epidemic: in excess of normal (1 case of rabies in Newton) Endemic: Usual occurrence in a geographic area Time

  27. Hepatitis Outbreak • Marshfield, MA had an outbreak of hepatitis A. • How did they identify the source?

  28. What Might Provide Clues (hypotheses)? Door 2 Door 1 EC IN Door 3 Door 4 B LL Door 5 Done SM

  29. Interview Some Cases Back

  30. Epidemic Curve Back

  31. Spot Map –Residence of Hepatitis Cases Back

  32. Based on these clues: • Knowledge of biology of hepatitis A (transmission, incubation) • Time course: epidemic curve of “point source” • Diverse age, occupation, location • Interview with a series of cases & similarities in restaurant use They hypothesized that the source was probably an infected food handler at: Rick’s Deli McDonald’s Jaime’s Pub Papa Gino’s Friendly’s

  33. Time • Dates of onset • Incubation period

  34. In a continuous common source epidemic, exposure to the source is prolonged over an extended period of time and may occur over more than one incubation period. The down slope of the curve may be very sharp if the common source is removed or gradual if the outbreak is allowed to exhaust itself. Cholera incubation period = 1-3 days

  35. In a point source epidemic, persons are exposed to the same source over a limited, defined period of time, and all of the new cases occur within the span of one incubation period.  Incubation period Hepatitis A incubation period = 15-50 days (mean=30) DPH Report: “This sudden increase in reported cases in the Marshfield area led [us] to believe that the cases could be due to a common source of infection or an infected food handler [a point source] at a restaurant frequented by the cases.”

  36. Apropagated (progressive source) epidemicoccurs when a case of disease serves as a source of infection for subsequent cases and those subsequent cases, in turn, serve as sources for later cases. This can result in a series of successively larger peaks, reflective of the increasing number of cases caused by person-to-person contact, until the pool of susceptible people is exhausted or control measures are implemented.

  37. Marshfield Hepatitis Cases (Graphed in 2-day increments) Given the sharp increase and subsequent decline, which all occurred within <30 days, this is characteristic of a “point source”.

  38. Marshfield Hepatitis Cases (N=20) (Graphed in 1-day increments) Adapted from MDPH Report NOTE: The epidemic curve in the MDPH report included additional cases (N=33) who were not in the case-control study. They also graphed at one-day increments; with a relatively small outbreak, the number of cases varies a lot from day to day, and it is hard to appreciate the true shape of the epidemic curve.

  39. Descriptive information provides clues. • What factors might be associated with disease? • Are there similarities among the diseased? • Are there differences between diseased & well people? • What correlates with disease? • Person: characteristics? • Place: specific locations or settings? • Time: does it vary over time?

  40. Characteristics of person, place, & time also generate hypotheses about chronic diseases.

  41. Person: Characteristics of People With Disease Person Were they similar with respect to: • Age, gender, race • Socioeconomic status • Body weight • Physical activity • Family history • Diet • Occupation • Sexual history • Travel

  42. Characteristics of people with a disease Person Death rates from Coronary Artery Disease (Age-specific rates) AgeMalesFemales 5-14 0.9 0.8 15-24 2.6 1.6 25-34 9.4 4.2 35-44 60.6 16.2 45-54 265.6 71.2 55-64 708.7 243.7 65-74 1670.0 769.4 75-84 3751.5 2359.0 85+ 8596.0 7215.1

  43. Place Where Does It Occur? • Does frequency of disease vary with location? • from country to country? • from state to state? • among cities or neighborhoods? • in different parts of a large workplace?

  44. Highest Significantly higher Higher than average (NS) Average Lower than average Place Stomach Cancer Females [from Atlas of Cancer Mortality for U.S. Counties: 1950-1969, TJ Mason et al, PHS, NIH, 1975 Males

  45. Stomach Cancer Mortality in Japanese Stomach CancerMortality (/100,000 pop.) Japanese in Japan 58.4 Japanese immigrants to California 29.9 Sons of Japanese immigrants 11.7 Native Californians (Caucasians) 8.0

  46. Does the Rate of Disease Change Over Time? Time • Hasthe frequency of disease changed • over several decades? • Does frequency of disease vary in a cyclic way that relates to the seasons? • Has it changed over the course of days?

  47. Does It Vary Over Time? Time SARS In Toronto (2004) Isolation of exposed people, restricted hospital visits, strict control procedures. Control precautions re-adopted. Barrier precautions downgraded

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