DR Medhat MRCP

Cohort study
• Def :
- It`s an observational study of a group of subjects with specific disease or
characteristic (e.g smokers) who are followed up over a period of time to detect
complications or new events.
- This group may be compared with control group (e.g non-smokers).
- If this type of study requires follow up over several years , it may be prone to loss
of subjects.
- Persons exposed (a+b) to the suspected cause and those not exposed (c+d) are
followed prospectively over time to determine the rate of a disease or specific
event.
Incidence rate of outcome in the exposed group =
Incidence rate of outcome in non-exposed group =
126