Sex Specific Incidence Rates of Type 2 Diabetes and Its Risk Factors over 9 Years of Follow-Up: Tehran Lipid and Glucose Study

OBJECTIVE To investigate the population-based incidence of type 2 diabetes and its potential risk factors in a sex-split cohort of Iranian population. MATERIALS AND METHODS A total of 8400 non-diabetic participants, aged ≥20 years (3620 men and 4780 women) entered the study. Crude and age standardized incidence rates per 1000 person-years were calculated for whole population and each sex separately. Cox proportional hazard models were used to evaluate hazard ratios (HR) and 95% confidence intervals for all potential risk factors in both uni-variable and multivariable models. RESULTS During a median follow-up of 9.5 years, 736 new cases of diabetes were identified, including 433 women and 303 men. The annual crude and age-standardized incidence rates (95% CI) of diabetes in the total population were 10.6 (9.92-11.4) and 9.94 (7.39-13.6) per 1000 person-years of follow-up and the corresponding sex specific rates were 10.2 (9.13-11.4) and 9.36 (5.84-14.92) in men and 11.0 (9.99-12.0) and 10.1 (7.24-13.9) in women, respectively. In the multivariable model, the risk for incident diabetes was significantly associated with fasting and 2 hour post challenge plasma glucose as well as family history of diabetes in both men and women. However, among women, only the contribution of wrist circumference to incident diabetes achieved statistical significance [HR: 1.16 (1.03-1.31)] with waist/height ratio being marginally significant [HR: 1.02 (0.99-1.04)]; while among men, only body mass index was a significant predictor [HR: 1.12 (1.02-1.22)]. Additionally, low education level conferred a higher risk for incident diabetes only among men [HR: 1.80 (1.23-2.36); P for interaction with sex = 0.003]. CONCLUSION Overall, sex did not significantly modify the impact of risk factors associated with diabetes among Iranian adults; however, among modifiable risk factors, the independent role of lower education and general adiposity in men and central adiposity in women might require different preventive strategies.