Sex-Specific Incidence Rates and Risk Factors for Hypertension During 13 Years of Follow-up: The Tehran Lipid and Glucose Study

Background: Hypertension, with a prevalence of 25.6% is a serious public health concern in Iran. Objective: To investigate the population-based incidence of hypertension and its potential risk factors in Tehranian adults during a median follow-up of 13.1 years. Methods: A total of 6,533 non-hypertensive participants (women = 3,639), >= 20 aged years participated in the study. Crude and age-standardized incidence rates per 1000 person-years were calculated for each sex, separately. Multivariable Cox proportional hazard models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CI) for all potential risk factors. Results: The crude and age-standardized incidence rates (95% CI) of hypertension per 1000 person-years were 29.7 (27.8-31.6) and 34.9 (32.5-37.4) among men and 25.8 (24.3-27.3) and 38.7 (35.5-42.0) among women, respectively. The incidence rate of hypertension in younger age groups was higher among men. However, after the 4th decade, the incidence rate was higher among women. Significant interactions of sex with age groups, body mass index categories, marital status, hypertriglyceridemia and glycemic categories were found in multivariable analyses (all p-values < 0.05). In the multivariable model, the risk in both sexes was found to be significantly associated with older age, obesity, and normal or high normal blood pressure (BP). Moreover, factors such as being overweight [HR: 1.20 (1.00-1.44)], former smoking [2.15 (1.52-3.04)], hypertriglyceridemia [1.23 (1.06-1.43)] and pre-diabetes status [1.19 (1.02-1.39)] were significant predictors of incident hypertension among women. Central obesity was found to be a significant predictor among men [1.26 (1.03-1.54)]. The optimism-corrected Harrell's C index (95% CI) in the categorical adjusted model was 0.75 (0.74-0.79) among men and 0.75 (0.74-0.76) among women. Conclusion: In the Tehranian population, nearly 2.7% of total participants (3% of men and 2.6% of women) develop hypertension each year. Obesity and high BP levels are the main modifiable risk factors in both sexes. Hypertriglyceridemia, prediabetes and former smoking are risk factors for hypertension among women.