On the Estimation and Comparison of Lifetime Morbid Risks

It is shown that the Kaplan-Meier product limit estimator of lifetime morbid risks may yield unreliable estimates, and it is suggested that under a proper model, those methods can be replaced by the original Stromgren estimator which is almost equally simple, and more accurate.

Abstract

Lifetime morbid risks are usually determined either by the Kaplan-Meier product limit estimator or by simpler estimators such as the lifetime prevalence, the Weinberg method or the Schulz method, which can be considered an elaboration of the Weinberg method.We show that the Kaplan-Meier product limit estimator of lifetime morbid risk may yield unreliable estimates.Although the simplicity of the Schulz method and the Weinberg method is appealing, we suggest that under a proper model, those methods can be replaced by the original Strömgren estimator which is almost equally simple, and more accurate.Increased accuracy is achieved when the investigators have prior indication regarding the distribution of the ages at onset for those affected by the disorder, and even when that indication is vague and only limited knowledge of the distribution is available.