Is insulin resistance or diabetes mellitus associated with stroke? An 18-year follow-up study

Insulin resistance and/or diabetes are risk factors for coronary artery disease. However, it is still controversial whether they are associated with the development of stroke. A total of 304 Japanese men and women, aged 20-69 years, were selected on the basis of casual high blood glucose concentrations from 2732 participants of a population-based health examination in 1980. They all underwent a 50 g oral glucose tolerance test in 1981. Homa IR (index of insulin resistance) and Homa beta-cells (index of beta-cell function) were calculated from their fasting insulin and glucose using the formulas for the homeostasis model. They were followed-up for 18 years. Incidence of stroke was investigated by computed tomography. During 18 years, 28 subjects had a stroke; 21 had ischemic and nine had hemorrhagic strokes (two had both). Baseline variables, which showed an independent association with the incidence of stroke in the Cox proportional hazard model, were blood pressure, use of anti-hypertensive medications, and Homa beta-cell index (inversely) after adjustments for age and sex. After further adjustment for blood pressure using a step-forward method, Homa beta-cell was significantly related to the incidence of stroke (Hazard ratio: 0.65, 95% confidence interval: 0.44-0.95). In addition to hypertension, diabetes but not insulin resistance, is a risk factor for stroke.