Background and purpose: Non-insulin-dependent diabetes mellitus (NIDDM) is a major risk factor for stroke in the middle-aged population, but few prospective population-based studies are available in the elderly. Moreover, the importance of metabolic control and the duration of diabetes in diabetic subjects has remained controversial. There are no previous studies on association of insulin with the risk of stroke. The present study examined whether NIDDM, its metabolic control and duration, and insulin level predict stroke.
Methods: We measured cardiovascular risk factors including glucose tolerance, plasma insulin, and glycosylated hemoglobin A1c in a Finnish cohort of 1298 subjects aged 65 to 74 years and investigated the impact of these risk factors on the incidence of both fatal and nonfatal stroke during 3.5 years of follow-up.
Results: Of 1298 subjects participating in the baseline study, 1069 did not have diabetes and 229 had NIDDM. During the 3.5-year follow-up, 3.4% (n = 36) of nondiabetic subjects and 6.1% (n = 14) of NIDDM subjects had a nonfatal or fatal stroke. The incidence of stroke was significantly higher in diabetic women compared with nondiabetic women (odds ratio [OR], 2.25; 95% confidence interval [CI], 1.65 to 3.06). In contrast, the risk of stroke was not significantly higher in diabetic men than in nondiabetic men (OR, 1.36; 95% CI, 0.44 to 4.18). In multivariate logistic regression analyses including all study subjects, fasting and 2-hour glucose (P < .01 and P < .05, respectively), glycosylated hemoglobin A1c (P < .01), atrial fibrillation (P < .05), hypertension (P < .05), and previous stroke (P < .01) predicted stroke events. In diabetic subjects, fasting and 2-hour glucose (P < .01 and P < .05, respectively), glycosylated hemoglobin A1c (P < .05), the duration of diabetes (P < .05), and atrial fibrillation (P < .05) were the baseline variables predicting stroke events. Finally, fasting insulin (P < .05), hypertension (P < .05), and previous stroke (P < .01) were associated with stroke incidence in nondiabetic subjects.
Conclusions: Our 3.5-year follow-up study provides evidence that NIDDM, its metabolic control, and the duration of diabetes are important predictors of stroke in elderly subjects, particularly in women. Moreover, fasting insulin level appears to be a risk factor for stroke in elderly nondiabetic subjects.