Methods of adjustment for estimating the attributable risk in case-control studies: a review.

In the 1980's, progress was made in adjusting estimates of the attributable risk (AR) for confounding factors and in calculating associated confidence intervals. In this paper, methods of adjustment for estimation of the AR in case-control studies are reviewed. The limitations and problems associated with two methods based on stratification, the weighted-sum approach and the Mantel-Haenszel approach, are discussed. They include small-sample bias with the weighted-sum approach and the difficulty of taking interaction into account with the Mantel-Haenszel approach. A third method based on logistic regression is reviewed. It is argued that this latter method has the greatest generality and flexibility, and includes the two other approaches as special cases. Throughout the paper, an example of a case-control study of oesophageal cancer illustrates the use of the methods described.