Three methods used to measure association are 1) difference in proportions 2) relative risk 3) odds ratio. Odds ratio can only be applied on a 2x2 contingency table. Relative risk may be applied more generally.

The use of Odds ratio or relative risk depends on the design of the study. The relative risk is a ratio of two incidence rates or two mortality rates. and is an estimator of the excess risk among exposed as compared to non-exposed or less exposed. It is the standard way of risk assessment in cohort studies. The Odds ratio (OR) is a proxy estimate of the relative risk. Or is applied in case-control studies.

odds ratio for case control ( retrospective) studies and relative risk for cohort ( Prospective) studies

I agree with Dr. Omran. It depends on the study design. In the cohort studies, you can calculate the incidence directly, so you can safely calculate the relative risk, while you can't do that in the case-control studies, so you calculate the Odds ratio instead. In meta-analysis, when you draw the diagram comparing the RRs or ORs of different studies, with the line of value 1 in the middle, you can draw either of them.

odds ratio is calculated for case control studies, while relative risk is for cohort studies, so it depends on the study design.

Odds ratio is for case control studies and relative risk for cohort studies.

Odds ratio and relative risk can be both calculated in cohort study, while only odds ratio can be used in case-control study Good luck