[The risk of diabetes mellitus in relatives of diabetics treated with insulin].

The objective of this study was to compare the risk of diabetes mellitus in the relatives of type 1 (defined as cases diagnosed before 40 years and beginning insulin less than two years later) and in those of type 2 diabetics, treated with insulin. A random sample of 303 patients was obtained from responders to a postal survey sent to all 2800 diabetics living in the Oporto self county and identified as users of insulin the injection pen. After selecting those who completed the questions for sex, age, dates of diabetes diagnosis and of first insulin prescription, we were left with 192 index cases. They provided data concerning sex; age, and presence of diabetes for 1370 relatives (parents, siblings, offspring and spouses). The risk of diabetes (unspecified type) in family members was significantly lower in relatives of type 1 diabetics (OR = 0.31, CI 95%:0.19-0.48, p < 0.0005). This family risk was lower when the index case was a male (OR = 0.24, CI 95%:0.12-0.47 vs OR = 0.39, CI 95%:0.21-0.74) or for female relatives (OR = 0.22, CI 95%:0.11-0.42 vs OR = 0.43, CI 95%:0.22.-0.82). After adjustment for confounders applying logistic regression to each family stratum, the risk remained significantly lower for parents (OR = 0.35, CI 95%:0.17-0.71) and siblings of type 1 diabetics compared to similar relatives of type 2 cases (OR = 0.84, CI 95%:0.06-10.6) but was not significantly different for the offspring (OR = 0.68, CI 95%:0.11-4.17) or the spouses (OR = 0.84, CI 95%:0.06-10.6).(ABSTRACT TRUNCATED AT 250 WORDS)