Background: Type 2 diabetes mellitus (DM) is a well-known familial disease, although the genetics of this complex condition remains unclear. Recent evidence suggests the significance of maternal inheritance. However, the pattern of family aggregation and the influence of other family relatives on the mode of transmission in Chinese patients with diabetes are lacking.
Methods: We interviewed 449 patients (151 men and 298 women) with type 2 DM who were aged between 35 and 74 years with a mean age of 58 +/- 1 years in a referral hospital in central Taiwan. We recorded a detailed family history of diabetes for each patient.
Results: Overall, 60% of diabetic patients had at least one diabetic family member. Among these index patients, 22.5% had a diabetic mother compared with 12.0% who had a diabetic father (p < 0.001). Approximately 29% of diabetic patients had at least one diabetic sister compared with 24% who had at least one diabetic brother (p = 0.13). A total of 27% of diabetic men had a diabetic mother, compared with 20% of diabetic women. Women with diabetes had more diabetic sisters than did diabetic men. In contrast, diabetic men had a significantly increased percentage of diabetic family members on the maternal side or paternal uncles or aunts than did diabetic women. The percentage of diabetic patients who had a diabetic mother decreased as their age increased. The maternal effect disappeared in the diabetic patients who were over 65 years old. Statistical differences between diabetic fathers and mothers were observed when DM was diagnosed in patients under 65 years of age.
Conclusions: We documented the presence of family aggregation and significant maternal inheritance in Chinese patients with type 2 DM in Taiwan. Further prospective study is needed to monitor the offspring of diabetic parents and other relatives in order to clarify the true mode of family aggregation and maternal transmission of type 2 DM.