Sex-specific relations between fasting insulin, insulin resistance and incident hypertension: 8.9 years follow-up in a Middle-Eastern population

The purpose of this study was to investigate whether fasting serum insulin levels, homeostasis model assessment of insulin resistance (HOMA-IR) and insulin-to-glucose ratio (IGR) were associated with incident hypertension. In a prospective study, 4093 Iranian participants (1725 men and 2368 women) without hypertension and known diabetes at baseline (1999-2001) were followed for a median of 8.9 years. Regular follow-up examinations were performed at 3-year intervals. Multivariate Cox proportional hazard models were used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) of incident hypertension adjusting for sex, and in sex-stratified models. During the study, 896 incident cases of hypertension (432 men and 464 women) were identified (total incident rate: 27.5 per 1000 person-years). In the multivariable models, serum insulin level, HOMA-IR and IGR were positively associated with hypertension incidence, adjusting for sex. In the sex-stratified analyses, after adjusting for potential confounders, women in the highest quartile of insulin, HOMA-IR and IG had a significantly higher incidence of hypertension, compared with those in the lowest quartile (HR: 1.7 (95% CI 1.26-2.30); HR: 1.80 (95% CI 1.31-2.40) and HR: 1.67 (95% CI 1.26-2.22), respectively); among men, these relations were also significant, until including waist circumference and body mass index in the models (HR: 1.17 (95% CI 0.85-1.62), HR: 1.25 (95% CI 0.91-1.73) and HR: 1.06 (95% CI 0.77-1.45), respectively). Higher fasting serum insulin levels, HOMA-IR and IGR were associated with incident hypertension among women, whereas these associations were not significant after adjusting for obesity measures in men.