Age of onset, age at examination, and other covariates in the analysis of family data.

Information on age of onset can easily be incorporated into regressive logistic models by assuming that age of onset follows a logistic distribution. This is analogous to previously proposed models based on the normal distribution. The two distributions, and hence the two types of models, are very similar. In each case the generalized modules power transformation can be used as a basis for more flexibly modeling the age of onset distribution.