Cohort and case-control studies are two common types of observational analytical studies used in medical research. Cohort studies follow groups of individuals over time and compare outcomes between those exposed and unexposed to a particular risk factor. Case-control studies identify cases with an outcome and compare their exposures to controls without the outcome. Both study designs allow researchers to examine multiple exposures and outcomes simultaneously while accounting for potential confounding factors.

1. Case Control & Cohort
Observational Studies
Edited by : Dr. Nermin Osman
Assistant lecturer of Medical Statistic
Medical Research Institute, Alexandria University
United Nations System Staff College Intern-UNITAR

2. Research designs
Secondary
Research
Designs
Systematic
Review/Meta
analysis
Primary
Research
Designs
Descriptive
Cross-
sectional
(survey)
Qualitative Case Report Case Series
Analytical
Experimental
RCT
Controlled
Clinical Trial
Observational
Cohort
Case-control
3

3. Levels of Evidence
Systemat
ic Review
with MA
Systematic
Review
Double-blind RCT
RCT without blinding
Non-Randomised Controlled
Trial
Cohort Study
Case-Control Study
Cross-sectional Survey
Case Report / Case Series
Expert Opinion

15. Figure 1.Representation of the reference time points for
exposure data and outcomes of interest in cohort studies.

23. Confounders

28. Odds ratio Relative risk