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Aug 9, 2023 · The odds ratio is mathematically similar to the risk ratio when the outcome is rare, because A+B will be similar to B, and C+D will be similar to D. But when the outcome is common, the odds ratio and risk ratio can be very different.1.
Odds ratios frequently are used to present strength of association between risk factors and outcomes in the clinical literature. Odds and odds ratios are related to the probability of a binary outcome (an outcome that is either present or absent, such as mortality).
- Edward C. Norton, Bryan E. Dowd, Matthew L. Maciejewski
- 2018
The risk ratio gives the relative increase or decrease in the risk (or prevalence) of the outcome given a particular exposure or treatment; the odds ratio is similar but gives the relative increase or decrease in the odds.
The risk difference (RD) is the difference between the absolute risks of 2 interventions or risk factors. The RD represents excess risk attributed to the group with the higher risk. The odds ratio can estimate the risk ratio when the probability of an event is ≤10%.
Relative risk can be directly determined in a cohort study by calculating a risk ratio (RR). In case-control studies, and in cohort studies in which the outcome occurs in less than 10% of the unexposed population, the OR provides a reasonable approximation of the RR.
- Anthony J. Viera
- 2008
Measures of relative effect express the outcome in one group relative to that in the other. The risk ratio (or relative risk) is the ratio of the risk of an event in the two groups, whereas the odds ratio is the ratio of the odds of an event (see Box 9.2.a).
odds ratios approximate relative risk ratios, when the outcomes are not rare, odds ratios always overestimate relative risk ratios, a problem that becomes more acute as the baseline prevalence of the outcome exceeds 10%. Odds ratios cannot be calculated directly from relative risk ratios. For example, an odds ratio for
