Diabetes, fasting glucose levels, and risk of ischemic stroke and vascular events: findings from the Northern Manhattan Study (NOMAS).

OBJECTIVE: There is insufficient randomized trial data to support evidence-based recommendations for tight control of fasting blood glucose (FBG) among diabetic subjects in primary stroke prevention. We explored the relationship between FBG among diabetic subjects and risk of ischemic stroke in a multiethnic prospective cohort. RESEARCH DESIGN AND METHODS: Medical and social data and FBG values were collected for 3,298 stroke-free community residents: mean age +/- SD was 69 +/-10 years; 63% were women, 21% were white, 24% were black, and 53% were Hispanic; and follow-up was 6.5 years. Baseline FBG levels were categorized: 1) elevated FBG: history of diabetes and FBG >or=126 mg/dl (7.0 mmol/l); 2) target FBG: history of diabetes and FBG <126 mg/dl (7.0 mmol/l); or 3) no diabetes/reference group. Cox models were used to calculate hazard ratios (HRs) and 95% CI for ischemic stroke and vascular events.
RESULTS: In the Northern Manhattan Study, 572 participants reported a history of diabetes and 59% (n = 338) had elevated FBG. Elevated FBG among diabetic subjects was associated with female sex (P < 0.04), Medicaid (P = 0.01), or no insurance (P = 0.03). We detected 190 ischemic strokes and 585 vascular events. Diabetic subjects with elevated FBG (HR 2.7 [95% CI 2.0-3.8]) were at increased risk of stroke, but those with target FBG levels (1.2 [0.7-2.1]) were not, even after adjustment. A similar relationship existed for vascular events: elevated FBG (2.0 [1.6-2.5]) and target FBG (1.3 [0.9-1.8].
CONCLUSIONS: This prospective cohort study provides evidence for the benefits of tighter glucose control for primary stroke prevention.