relative risk

Syllable breakdown

Dictionary meaning

a measure of association also called the risk ratio, defined as the probability of an outcome in an exposed group divided by the probability of the outcome in an unexposed group in a cohort or experimental study; a relative risk of 2.0 means the exposed group has twice the probability of developing the outcome compared to the unexposed group; a relative risk of 0.5 means exposure is associated with half the probability of the outcome — a protective effect; unlike the odds ratio, the relative risk is directly interpretable as a ratio of probabilities rather than a ratio of odds, making it more intuitive when communicating risk to clinicians and the public; however, relative risk is only estimable from cohort studies and randomised trials where incident cases are counted in defined populations at risk — it cannot be estimated directly from case-control studies; the relative risk can be misleading when presented without absolute risk information — a doubling of a very small risk may be less clinically significant than a 10 percent increase in a large risk

Examples

• The relative risk of stroke among oral contraceptive users was 1.8, meaning an 80 percent higher probability compared to non-users.
• Presenting the relative risk without the absolute baseline risk can exaggerate the clinical significance of a finding.

Synonyms: risk ratio, RR