Agency for Healthcare Research and Quality website page on odds ratios:. Definition: The chance of an event occurring in one group compared to the chance of it occurring in another group. The odds ratio OR is a measure of effect size and is commonly used to compare results in clinical trials.
Example: For example, a research study compared two groups of women who developed diabetes during their pregnancies. One group was treated with metformin, and the other group was treated with insulin. The researchers recorded how many of the mothers delivered their babies earlier than expected less than 37 weeks after becoming pregnant.
When they calculated the odds of an early delivery, the odds ratio OR for metformin was 1. This means that the women taking metformin had a small increase 1.
I told him that a journalist had recently asked me:. I write about studies on a daily basis and avoid citing odds ratios.
Instead I try to get researchers to covert them to more understandable numbers when possible. What do you think? Should odds ratios be reported as being the same as relative risk? Should they be reported at all? When we think about the relative effect of two competing approaches tests, drugs, interventions, etc , we are intuitively thinking about what is mathematically known as the risk ratio. The RR is therefore 0. Of course some people use OR even when RR is statistically appropriate — which is a bit like cheating; they do this because OR always looks more impressive than RR.
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Nurminen M. Analysis of epidemiologic case-base studies for binary data. Stat Med ; 8: — Interpretation and estimation of summary ratios under heterogeneity. Stat Med ; 1: — Assessment of excess risk in case-base studies. Practical considerations in choosing between the case-cohort and nested case-control designs. Epidemiology ; 2: — Wacholder S, Boivin J-F.
External comparisons with the case-cohort design. Rothman KJ. Modern epidemiology. Prentice R. Use of the logistic model in retrospective studies. Biometrics ; — Prentice RL. A case-cohort design for epidemiologic cohort studies and disease prevention trials. Biometrika ; 1— Risk ratio and rate ratio estimation in case-cohort designs: Hypertension and cardiovascular mortality. Download references. You can also search for this author in PubMed Google Scholar.
Correspondence to Markku Nurminen. Reprints and Permissions. Nurminen, M. To use or not to use the odds ratio in epidemiologic analyses?. Eur J Epidemiol 11, — Download citation. Accepted : 03 March Issue Date : August Anyone you share the following link with will be able to read this content:. Sorry, a shareable link is not currently available for this article.
Provided by the Springer Nature SharedIt content-sharing initiative. Skip to main content. Search SpringerLink Search. Abstract This paper argues that the use of the odds ratio parameter in epidemiology needs to be considered with a view to the specific study design and the types of exposure and disease data at hand.
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Deeks J. When can odds ratios mislead? Odds ratios should be used only in case-control studies and logistic regression analyses. BMJ —7. PLoS Med 6:e Grant MJ, Booth A. A typology of reviews: an analysis of 14 review types and associated methodologies. Health Info Libr J — Aviva P, Watson P. Statistics for Veterinary and Animal Science. London: Wiley-Blackwell What variables are important in predicting bovine viral diarrhea virus? A random forest approach. Vet Res Making BUGS open. R News —7.
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