Abstract
Odds ratios (ORs) and relative risks (RRs) are sensitive to the length of follow-up. In meta-analyses, pooling such results from studies with different lengths of follow-up may lead to an artificial heterogeneity and discrepancy caused by the choice of the summary index. In this article, we explore the utility of a meta-analysis method that uses the ratio of logarithms of survival probability as the measure of association, and that avoids the problems mentioned above when hazards are proportional. Meta-analyses of ORs, RRs and ratios of logarithms of survival probability are compared through a simulation study, in which data are simulated from a proportional hazard model and the length of follow-up varies across studies using realistic patterns of variability. Results show that the heterogeneity increases with the variability of length of follow-up for OR and RR, but not for the ratio of the logarithms of survival probability. A published meta-analysis is used to illustrate the method.
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