Family history of Japanese patients with non-insulin-dependent diabetes. Different implications of diabetes in parents and in siblings.

The family history of diabetes in parents and siblings was analyzed in relation to the age of onset and previous obesity in patients with non-insulin-dependent diabetes mellitus (NIDDM). The frequency of a positive family history of diabetes in parents was higher in patients with the onset of diabetes earlier than 40 years of age than in those who developed diabetes after 50 years of age (32% vs 12%, p less than 0.001). The frequency of a positive family history in siblings was about 20% and fairly constant in patients who became diabetic after 30 years. The prevalence of diabetes in siblings was higher in patients with diabetic parents than in those without diabetic parents (p less than 0.001). The higher frequency of diabetes in parents of young-onset patients remained significant even in a comparison of patient groups of similar ages (50-59 years) at the interview. Patients with definite obesity in the past had a significantly lower frequency of family history of diabetes in parents (p less than 0.001), and a lower prevalence of diabetes in their parents (p less than 0.001) and siblings (p less than 0.05) than did patients without obesity. The frequency of patients who had diabetic siblings did not differ between obese and lean groups. These data suggest that implications of the presence of diabetes in parents and in siblings are different in family history studies.(ABSTRACT TRUNCATED AT 250 WORDS)