odds ratio

Syllable breakdown

Dictionary meaning

a measure of association between an exposure and an outcome in epidemiological research, defined as the ratio of the odds of exposure among cases to the odds of exposure among controls in a case-control study, or equivalently as the ratio of the odds of disease among exposed to the odds of disease among unexposed in a cohort or cross-sectional study; the odds ratio of 1.0 indicates no association; greater than 1.0 indicates a positive association — exposure associated with increased outcome; less than 1.0 indicates a negative or protective association; the odds ratio approximates the relative risk when the disease is rare — the rare disease assumption — because in rare disease settings the odds of disease closely approximate the probability of disease; logistic regression is the standard statistical method for estimating odds ratios while adjusting for multiple confounders; interpretation requires distinguishing the odds ratio from the relative risk, which it overestimates when the outcome is common

Examples

• The odds ratio for lung cancer among smokers versus non-smokers was 14, indicating a 14-fold higher odds of cancer in smokers.
• An odds ratio of 0.6 for cardiovascular disease in statin users suggests a protective effect, reducing the odds by 40 percent.

Synonyms: OR