The role of insulin in age-related sex differences of cardiovascular risk profile and morbidity

Metabolic changes and shifts in vascular risk profiles during and after menopause may partly explain the loss of premenopausal protection against cardiovascular disease (CVD). The current population-based survey addresses changes in risk factors and insulin levels across an age range of 40-79 years in men and women. Population recruitment was performed as part of the Bruneck Study from July to November 1990. In brief, of 1000 subjects randomly selected for inclusion 936 participated, with insulin measurements available in a random subgroup of 880 men and women, 60 of whom were excluded due to manifest diabetes mellitus. Insulin concentrations were assessed according to Hales and Randle and by a human insulin-specific radioimmunoassay. A rise in insulin concentrations with advancing age in women (5th-8th decade, 10.5-14.4 mU/l or + 1.2%/year) contrasts with a marked gradual decline in insulin levels in men (5th-8th decade, 12.5-5.9 mU/l or - 2.4%/year). Age trends of insulin concentrations in sexes emerged as independent of age-related changes in body weight, type of fat distribution, alcohol consumption, cigarette smoking, social status, fasting glucose, and physical activity (P < 0.001 for sex-specific difference in the regression slopes). Insulin levels in pre- and postmenopausal women of equal age differed significantly (10.1 vs. 13.9 mU/l;, P = 0.003), thus advocating that variations of insulin observed may in part be related to shifts in sex hormone status. Levels of virtually all vascular risk atributes were lower in premenopausal women than in men of equal age, but the opposite was true for the elderly. The switch in the sex preponderance of vascular risk factors may be crucially involved in closing the CVD incidence gap between genders after menopause. The analysis suggests that variations in insulin levels are a common metabolic basis for sex/age trends in fasting glucose, apolipoprotein B, total cholesterol, total cholesterol/HDL cholesterol ratio, LDL density (LDL cholesterol/apolipoprotein B), triglycerides and systolic blood pressure. (C) 1997 Elesevier Science Ireland Ltd.