B0895
Title: Effects of unobserved heterogeneity on methods for analysing prevalent cohort and current duration designs
Authors: Niels Keiding - University of Copenhagen (Denmark) [presenting]
Abstract: Time to pregnancy is the duration from the time a couple starts trying to become pregnant until they succeed. It is considered one of the most direct methods to measure natural fecundity in humans. Statistical tools for designing and analysing time to pregnancy studies belong to the general area of survival analysis, but several features require special attention. Recruiting at incidence is difficult to carry out, so that prospective follow-up is more realistically achieved in a prevalent cohort design. Retrospective (pregnancy-based) designs, widely used in this area, do not allow efficiently including couples remaining childless. The current duration design starts from a cross-sectional sample of couples currently trying to become pregnant, using the backward recurrence time as basis for the estimation of time to pregnancy or time to the end of the pregnancy attempt. On the basis of a simulation study, it is studied the effect of unmeasured population heterogeneity on estimates of the distribution of time to pregnancy and of the effect of risk factors. The generality of such properties for prevalent cohort and current duration designs are briefly discussed.
