Family history and risk of insulin-dependent diabetes mellitus: a population-based case-control study.

Insulin-dependent diabetes mellitus (type 1) is a common chronic disease of childhood occurring throughout the world. In the literature, its most important determinants include genetic, environmental and familial factors. We evaluated family history as a determinant of the risk of type 1 diabetes mellitus with a population-based case-control study. Information about type 1 patients was taken from the dedicated register of the Abruzzo Region; the register has been collecting incident cases in the age group 0-14 years, diagnosed between 1 January 1990 and 31 December 1996. The control group was taken from the lists of patients attending family pediatricians. The family history data for type 1 and type 2 patients was obtained by a questionnaire, administered to their parents. The risk of type 1 diabetes mellitus associated with its occurrence in first- and second-degree relatives was estimated using logistic regression methods. Our results show that the risk is indeed increased with a positive family history (OR=3.96; 95% CI 1.54-10.14). This shows that the risk of type 1 diabetes mellitus for children whose fathers are affected by the disease is 11 times higher with respect to controls. Moreover, the risk for children whose brothers are affected by the disease is 20 times higher with respect to controls. In contrast, a family history for type 2 diabetes mellitus does not influence the risk.