Disadvantage of cohort study

• Cohort studies describe incidence or natural history.

• They analyse predictors (risk factors) thereby enabling calculation

of relative risk.

• Cohort studies measure events in temporal sequence

thereby distinguishing causes from effects.

• Retrospective cohorts where available are cheaper and

quicker.

• Confounding variables are the major problem in analysing

cohort studies.

• Subject selection and loss to follow up is a major potential

cause of bias.