Hss4303b – intro to epidemiology

1. Hss4303b – intro to epidemiology April 1, 2010 – a hodgepodge of stuff

2. Last time… • Type I error • Incorrectly rejecting the null • Type II error • Incorrectly failing to reject the null

3. Last time • Alpha relates to Type I error • Typically set at 0.05 • Beta relates to Type II error • Typically set at 0.20 Power = 1- beta

4. Last time • For 1-group study, and with alpha=0.05 and beta=0.20 N = 8 sigma2 / delta2 (approximately)

5. Last time • For 2-group study, and with alpha=0.05 and beta=0.20 Nper group = 16 sigma2 / delta2 (approximately)

6. Last time • What is delta? • The smallest difference worth detecting

7. Example • A cohort of 25 people is given an IQ test and scores an average of 138. After one year of intensive education, a similar IQ test is re-applied. The literature suggests that the standard deviation of the change in IQ should be 5. What is the smallest change in IQ that the cohort will be able to detect? Delta = square root [8variance/N] = square root [8x25/25] = 2.8

8. Posters

10. Your posters • New document uploaded to website • Poster is a visually presented research paper, but isn’t just a paper pasted onto a wall • Half of the 25 marks I will assess before the poster day • The other half will be awarded by judges on the day • I need to receive via email the text of your posters (just the text!) by midnight Thursday April 8th • Send to hss4303@gmail.com • Failure to send on time will be penalized 2.5 of the total 25 marks for each 24 hour period it is late

11. From association to causation • Approaches to etiology • Types of etiological associations • Types of causal relationships • Evidence of causal relationship • Examples of causal relationship • Peptic ulcers and gastric cancers • Alcohol use and abuse • Estrogen use and Alzheimer’s disease

12. Approaches to etiology • In-vitro studies • Cell culture or organ cultures • In-vivo studies • Animal studies • Acute exposures • Chronic exposures • Human studies • Unplanned experiments • Natural experiments

13. Etiological studies • Approaches to studying disease etiology • Animal studies • In-vitro studies • Population studies • Observation studies • Chernobyl disaster • Bhopal tragedy • Hiroshima and Nagasaki study

14. Association studies • Examination of association • If there is association; nature of this association Observed association between exposure and disease

15. Anatomy of etiological studies A frequent sequence of studies in human populations.

16. Ecologic studies Correlation between dietary fat intake and breast cancer by country

17. Ecologic studies • ____________ studies • Show plausibility of relationship • Does not establish causality • Does not take into account variability of exposure among individuals • Ecologic fallacy • Ascribing to members of a group, characteristics that they in fact do not possess individually

18. Causal relationship • Types of causal relationships • Direct • A factor directly causes a disease • Indirect • A factor causes a disease through intermediate factor or factors

19. Different possibilities of causal relationship • Necessary and sufficient • Necessary but not sufficient • Sufficient but not necessary • Neither sufficient nor necessary Host Agent Medium

20. Possibilities in causal relationship • Necessary and sufficient • A one to one relationship of exposure to disease, rarely if ever occurs • Infection with corona virus H5N1 and development of SARS Types of causal relationships: I. A factor is___________________________.

21. Possibilities in causal relationship • Necessary but not sufficient • One or more factors are essential and necessary, but not, in itself, sufficient to cause the disease • An initiator and promoter are both necessary to cause cancer but each on its own do not cause cancer Types of causal relationships: II. Each factor is ________________________.

22. Possibilities in causal relationship • Sufficient but not necessary • One or more factors (by themselves) can cause the disease • Radioactivity exposure or benzene exposure can each produce leukemia without the presence of the other Types of causal relationships: III. __________________________________.

23. Possibilities in causal relationship • Neither sufficient nor necessary • A complex interaction between factors, so no essential or required factors can be identified • Hormonal changes, xenobiotics, chronic inflammation, dietary factors and age are intricately involved in the development of prostate cancer Types of causal relationships: IV. __________________________________________.

24. CSEB • We welcome student members • The latest newsletter is now on the class website • Features articles by your TA and one of your classmates

25. Epidemiology around the world http://www.youtube.com/watch?v=AW-ZHpFrLZQ CAREC

28. WHO Epidemiology • http://www.who.int/topics/epidemiology/en/ • Fact sheets • Global health atlas • Weekly epidemiology report • etc

29. Weekly Epidemiology Record • http://www.who.int/wer/en/ • “The Weekly Epidemiological Record (WER) serves as an essential instrument for the rapid and accurate dissemination of epidemiological information on cases and outbreaks of diseases under the International Health Regulations and on other communicable diseases of public health importance, including emerging or re-emerging infections. “

33. The CDC • Lots of fun tidbits on their website: • www.cdc.gov CDC Tracking network: • http://www.youtube.com/watch?v=J42CLZH1NlE CDC outbreak response • http://www.cdc.gov/CDCTV/RespondOutbreaks/index.html

34. Epi Info • Free epidemiology software created by the CDC • http://www.cdc.gov/epiinfo/

40. Erin’s Hours • No more formal tutorials except for two exam review sessions: • April 22 • April 26 (afternoon)