Obtaining adjusted prevalence ratios from logistic regression models in cross-sectional studies

Cad Saude Publica. 2015 Mar;31(3):487-95. doi: 10.1590/0102-311x00175413.

Abstract

In the last decades, the use of the epidemiological prevalence ratio (PR) instead of the odds ratio has been debated as a measure of association in cross-sectional studies. This article addresses the main difficulties in the use of statistical models for the calculation of PR: convergence problems, availability of tools and inappropriate assumptions. We implement the direct approach to estimate the PR from binary regression models based on two methods proposed by Wilcosky & Chambless and compare with different methods. We used three examples and compared the crude and adjusted estimate of PR, with the estimates obtained by use of log-binomial, Poisson regression and the prevalence odds ratio (POR). PRs obtained from the direct approach resulted in values close enough to those obtained by log-binomial and Poisson, while the POR overestimated the PR. The model implemented here showed the following advantages: no numerical instability; assumes adequate probability distribution and, is available through the R statistical package.

MeSH terms

  • Cross-Sectional Studies / methods*
  • Humans
  • Logistic Models*
  • Models, Statistical*
  • Odds Ratio
  • Prevalence*
  • Probability*