INFLUENCE OF INSULIN, SYMPATHETIC NERVOUS-SYSTEM ACTIVITY, AND OBESITY ON BLOOD-PRESSURE - THE NORMATIVE AGING STUDY

Objective To examine the association of insulin and sympathetic nervou s system activity with blood pressure elevation in a cross-sectional s tudy of 752 nondiabetic male participants of the Normative Aging Study , aged 43-90 years. Methods Testing included a physical examination, m edical history, fasting and post-carbohydrate insulin and glucose leve ls determinations, an anthropometric examination, and 24 h urine colle ction for catecholamine level determination, Total obesity was represe nted by body mass index, central obesity by the abdomen circumference: hip circumference ratio, and sympathetic nervous system activity by 24 h urinary excretion of norepinephrine. Results Systolic and diastolic blood pressure (SEP and DBP, respectively) were positively related to body mass index, abdomen:hip ratio, norepinephrine excretion, and ins ulin levels in univariate analyses, The relationship between insulin l evel and SEP and DBP persisted after adjustment for body mass index, a bdomen:hip ratio, norepinephrine, age, smoking, physical activity leve l, and antihypertensive medication use, The norepinephrine level was r elated to SEP and DBP after adjustment for insulin level, age, smoking , physical activity level, and antihypertensive medication use, and th ese relationships remained marginally significant after further adjust ment for body mass index and abdomen:hip ratio, In contrast, neither b ody mass index nor abdomen:hip ratio were related to blood pressure af ter adjustment for insulin level, Among participants in the lowest ter tiles both of insulin and of norepinephrine levels, 10% were hypertens ive, compared with 35% in the highest tertiles of these variables. In a multiple logistic regression model, insulin level, norepinephrine le vel, and an interaction term for insulin level with norepinephrine exc retion were independent predictors of hypertension. Conclusions The re sults suggest that insulin level and sympathetic nervous system activi ty are associated with hypertension among middle-aged and elderly men.