Lecture 1 - Introduction to Epidemiology

Epi slids

1. EXTRA SLIDES EPI 500

2. Case Definition: COVID19 https://ndc.services.cdc.gov/case-definitions/coronavirus-disease-2019-2020-08-05/

3. Estimated rate ratio of in-hospital death for Friday, Saturday and Sunday stays, above and beyond the effect of length of stay, over the course of hospitalisation for typical patients admitted on a Monday (day 1) and hospitalised for 22 days. Samy Suissa et al. Eur Respir J 2014;44:627-633

4. Prevalence The proportion of the population who has existing cases of a disease at a particular point in time or over a period of time. A snapshot of time (cross-sectional) Example: 11% of the US population age >65 years or older has Alzheimer’s Disease (One in nine). Almost 2/3 rd are women Alzheimer’s Association, 2021

5. Odds Odds of an event= the ratio of the probability that an event will occur, to the probability that the event will not occur. p/1-p Easier to calculate and interpret Example: If the probability of diabetes in a patient is 5%m then the odds of diabetes are 0.05/(1-0.05) = 0.052 = 1:19

6. Measures of frequency and Association Open Epi: http://www.openepi.com/Menu/OE_Menu.htm Measures of Frequency  Measures of Association Risk Risk Ratio Risk Difference Rate Rate Ratio Rate Difference Prevalence Prevalence Ratio Prevalence Difference Odds Odds Ratio

7. Hierarchy of Evidence Pyramid

8. ACTIVE INTERVENTION GROUP COMPLIERS, NONCOMPLIERS OUTCOMES COMPARISON GROUP COMPLIERS, NONCOMPLIERS OUTCOMES REFERENCE POPULATION (population to whom results generalizable) EXPERIMENTAL POPULATION (population in whom study is done) PARTICIPANTS (willing and eligible) RANDOME ALLOCATION NONPARTICIPANTS

9. ACTIVE GROUP COMPLIERS NONCOMPLIERS OUTCOMES OUTCOMES (a) (b) COMPARISON GROUP COMPLIERS NONCOMPLIERS OUTCOMES OUTCOMES (c) (d) STUDY PARTICIPANTS PRIMARY ANALYSIS: Intention-to-treat analysis: "Once randomized, always analyzed". ( a+b ) versus ( c+d ) SECONDARY ANALYSIS: Compliers-only analysis: (a) versus (c). But beware - this is not a randomized comparison. ANALYSIS

10. Effectiveness of montelukast for Atopic Dermatitis

11. Phases of clinical trials for Vaccine development Source: https://covid19community.nih.gov/resources/understanding-clinical-trials

12. https://www.nejm.org/doi/full/10.1056/nejmoa2034577