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JAMA Guide to Statistics and Methods
September 15, 2020

Estimating Risk Ratios and Risk Differences: Alternatives to Odds Ratios

Author Affiliations
  • 1Research Center for Emergency Medicine, Department of Clinical Medicine, Aarhus University and Aarhus University Hospital, Aarhus, Denmark
  • 2Department of Cardiology, Viborg Regional Hospital, Viborg, Denmark
  • 3Prehospital Emergency Medical Services, Central Denmark Region, Denmark
  • 4Department of Anesthesiology and Intensive Care, Aarhus University Hospital, Aarhus, Denmark
JAMA. 2020;324(11):1098-1099. doi:10.1001/jama.2020.12698

The goal of many medical research studies is to estimate the direction and magnitude of the effect of an intervention or treatment on a clinical outcome (in clinical trials) or the association between an exposure and an outcome (in observational studies). This effect or association can be presented in various forms, depending on the measured outcome. For example, if the outcome is a continuous measure (eg, blood pressure), the effect or association could be represented as a mean difference between the groups. If the outcome is a time-to-event outcome (eg, time to death), the effect or association is often expressed as a hazard ratio.