Associations of parental history of diabetes mellitus with the offspring's incidence is modified by offspring's body weight, findings from a Japanese worksite-based cohort
METHODS: Subjects were 4,446 Japanese workers (3,492 men and 954 women) without a history of diabetes at baseline. Parental history of DM was self-reported separately for father and mother. Type 2 DM (T2DM) incidence was ascertained from 2002 through 2011 by annual health check-ups and self-reports. Cox proportional hazard model adjusted for sex, smoking (current, never, past), frequency of ethanol consumption (times/week), body mass index (BMI, kg/m2), physical activity (yes/no) was used to estimate hazard ratios (HRs) and the 95% confidence intervals (95% CIs) of the parental history groups. Stratified analyses by sex and overweight (BMI >= 25 kg/m2) were performed, and the interaction was tested by likelihood ratio tests.
RESULTS: During the follow-up, 277 cases (227 men, 50 women) of T2DM (incidence rate: 7.94 per 1000 person-year) were observed. The HRs (95% CIs) of diabetes history in father, mother, and both parents compared to neither were 1.73 (1.21 – 2.48), 1.72 (1.11 – 2.67), and 3.12 (1.28 – 7.58), respectively. Stratified analysis by overweight revealed that there was an increased risk of T2DM associated with maternal history in normal weight subjects (incidence rate: 5.2 vs. 13.2 per 1000 person-year, HR: 2.57, 95% CI: 1.61 – 4.12), not in overweight subjects (incidence rate: 14.2 vs. 12.8 per 1000 person-year; HR: 0.86, 95% CI: 0.40 – 1.86, P for multiplicative interaction = 0.014). The same pattern was not observed for paternal history of DM and overweight.
CONCLUSIONS: Maternal history of DM increased offspring’s risk of T2DM in normal weight subjects to a degree that was observed in overweight subjects in middle-aged male and female workers in Japan.