Estimating effects of probands' characteristics on familial risk: I. Adjustment for censoring and correlated ages at onset

Family studies with age at onset of the disease as the endpoint face two important problems: censoring and correlation of age at onset among relatives. We present a multivariate survival model for ages at onset of relatives which incorporates the problems cited above. The interpretations of regression coefficients and association parameter in the context of family studies are emphasized. The present paper describes a statistical method for estimating these parameters. In a companion paper [Pulver and Liang, Genet Epidemiol 8:339–350, 1991] this model is applied to a genetic epidemiologic study of schizophrenia.