Prospective associations of fasting insulin, body fat distribution, and diabetes with risk of ischemic stroke

OBJECTIVE - We tested the hypothesis that diabetes, body fat distribution, and (in nondiabetic subjects) fasting insulin levels are positively associa ted with ischemic stroke incidence in the general population RESEARCH DESIGN AND METHODS - As part of the Atherosclerosis Risk in Communities (AR IC) Study we measured diabetes by using fasting glucose criteria, waist and hip circumferences, and fasting insulin levels with a radioimmunoassay in >12,000 adults aged 45-64 years who had no cardiovascular disease at baseli ne. We followed them for 6-8 years for ischemic stroke occurrence (n = 191) . RESULTS - After adjustment for age, sex, race, ARIC community, smoking, and education level, the relative risk of ischemic stroke was 3.70 (95% CI 2.7 -5.1) for diabetes, 1.74 (1.4-2.2) for a 0.11 increment of waist-to-hip rat io, and 1.19 (1.1-1.3) for a 50-pmol/l increment of fasting insulin among n ondiabetic subjects. Ischemic stroke incidence was nor statistically signif icantly associated with BMI (comparably adjusted relative risk = 1.15, 95% CI 0.97-1.36). With adjustment for other stroke risk factors (some of which may mediate the effects of diabetes, fat distribution, and hyperinsulinemi a), the relative risks for diabetes, waist-to-hip ratio, and fasting insuli n level were 2.22 (95% CI 1.5-3.2), 1.08 (0.8-1.4), and 1.14 (1.01-1.3), re spectively CONCLUSION - Diabetes is a strong risk factor for ischemic stroke. Aspects of insulin resistance, as reflected by elevated waist-to-hip ratios and ele vated fasting insulin levels, may also contribute to a greater risk of isch emic stroke.