Question

What are the benefits and downsides of an odds ratio? What are the benefits and downsides of a relative risk? Why are each used in different studies?

Answer 1

Answer:

1. Odd ratio:

- Advantages:  May be reported in cohort studies, case-control designs and clinical trials.  

- Disadvantages: Bad estimation of the risk in situations where the initial risk is high. Difficult to interpret.  

2. Relative risk:

- Advantages: Easy to interpret.  

- Disadvantages: Not available for case-control designs. Adjustment of the covariance is a hard task.

Explanation:

An odds ratio is a statistical measure used to compare the relative odds of the event/outcome (disease or disorder) with respect to a given variable of interest (e.g. medical history). An odd ratio may be interpreted as though it was a relative risk and therefore this value may lead to error. On the other hand, a relative risk (RR) is a statistic that measures the ratio between the likelihood of an event in an exposed group (disease or disorder) with respect to the likelihood of an event in an unexposed comparison group. Both statistics compare the relative probability of an event/outcome between two comparison groups. The relative risk can not be used in case-control designs because information about the total number of exposed people is not available.