Relative risks and odds ratios: Simple rules on when and how to use them

Dean P McKenzie; Christopher Thomas

doi:10.1111/eci.13249

Relative risks and odds ratios: Simple rules on when and how to use them

Eur J Clin Invest. 2020 Apr 20:e13249. doi: 10.1111/eci.13249. Online ahead of print.

Authors

Dean P McKenzie^{1

2}, Christopher Thomas¹

Affiliations

¹ Epworth HealthCare, Melbourne, Australia.
² Department of Statistics, Data Science and Epidemiology, Swinburne University of Technology, Melbourne, Australia.

PMID: 32311087
DOI: 10.1111/eci.13249

Abstract

Aim: Relative risks and odds ratios are widely reported in the medical literature, but can be very difficult to understand. We sought to further clarify these important indices.

Methods: We illustrated both relative risks and odds ratios using bar charts, then looked at the types of study for which each statistic is suited. We demonstrated calculation of relative risks and odds ratios through analysis of tabled data from a recent published longitudinal study, using a 2 × 2 table and R, the open-source statistical programming language. Simple rules for when and how to use relative risks and odds ratios are presented.

Conclusion: Understanding the difference between relative risks and odds ratios and when and how to use them may aid clinical interpretation, dissemination and translation of research findings.

Keywords: clinical research; communication; health promotion and prevention; research methods; statistics.