Analysis of case-cohort designs

The case-cohort design is most useful in analyzing time to failure in a lar ge cohort in which failure is rare. Covariate information is collected from all failures and a representative sample of censored observations. Samplin g is done without respect to time or disease status, and, therefore, the de sign is more flexible than a nested case-control design. Despite the effici ency of the methods, case-cohort designs are not often used because of perc eived analytic complexity. In this article, we illustrate computation of a simple variance estimator and discuss model fitting techniques in SAS. Thre e different weighting methods are considered. Model fitting is demonstrated in an occupational exposure study of nickel refinery workers. The design i s compared to a nested case-control design with respect to analysis and eff iciency in a small simulation. In this example, case-cohort sampling from t he full cohort was more efficient, than using a comparable nested case-cont rol design. (C) 1999 Elsevier Science Inc. All rights reserved.