[R] Cox regression for prevalence estimates

The Michaelson Institute hadasa704 at 012.net.il
Mon Sep 6 09:33:10 CEST 2004

Hello, I'm an MD working in an eye clinic. I'm learning by myself to use R
for use in my research works and for implementation in a software project.
There are some authors who recomends the use of Cox regression as a
substitute for Logistic regression (<a
href="http://www.biomedcentral.com/1471-2288/3/21.pdf"> Barros AJD, Hirakata
VN. BMCMedical Research Methodology, 2003; 3:21 </a>. The use of Cox
regression permit the estimation of the prevalence rates rather than Odds
ratios obtained by logistic regression analysis. 
Cox regression is used for time-to-event data. To obtain prevalence rates
the time has to be constant. One of the problems of Cox regression is that
the confidence intervals are overestimated. To correct this Barros &
Hirakata recommend the use of robust variance estimates.
How can R be used to calculate the prevalence ratios using Cox regression +
robust variance estimates ?

Thanks for your collaboration,

Tomas Karpati MD
The Michaelson Institute for Rehabilitation of Vision
Hadassah Medical Organization

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