## Odds ratios and risk ratios: what's the difference and why does it matter?

Publication ,  Journal Article
Viera, AJ
Published in: South Med J
July 2008

Odds ratios (OR) are commonly reported in the medical literature as the measure of association between exposure and outcome. However, it is relative risk that people more intuitively understand as a measure of association. 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. However, when an outcome is common (iY 10% in the unexposed group), the OR will exaggerate the RR. One method readers can use to estimate the RR from an OR involves using a simple formula. Readers should also look to see that a confidence interval is provided with any report of an OR or RR. A greater understanding of ORs and RRs allows readers to draw more accurate interpretations of research findings.

South Med J

1541-8243

July 2008

101

7

730 / 734

## Location

United States

• Risk
• Odds Ratio
• Humans
• General & Internal Medicine
• Cohort Studies
• Case-Control Studies
• 42 Health sciences
• 32 Biomedical and clinical sciences
• 11 Medical and Health Sciences

### Citation

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ICMJE
MLA
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Viera, A. J. (2008). Odds ratios and risk ratios: what's the difference and why does it matter? South Med J, 101(7), 730–734. https://doi.org/10.1097/SMJ.0b013e31817a7ee4
Viera, Anthony J. “Odds ratios and risk ratios: what's the difference and why does it matter?South Med J 101, no. 7 (July 2008): 730–34. https://doi.org/10.1097/SMJ.0b013e31817a7ee4.
Viera, Anthony J. “Odds ratios and risk ratios: what's the difference and why does it matter?South Med J, vol. 101, no. 7, July 2008, pp. 730–34. Pubmed, doi:10.1097/SMJ.0b013e31817a7ee4.
Viera AJ. Odds ratios and risk ratios: what's the difference and why does it matter? South Med J. 2008 Jul;101(7):730–734.

South Med J

1541-8243

July 2008

101

7

730 / 734

United States