Impaired glucose tolerance increases stroke risk in nondiabetic patients with transient ischemic attack or minor ischemic stroke

Background and Purpose - Impaired glucose tolerance, an intermediate metabolic state between normal glucose and diabetes characterized by nonfasting glucose levels between 7.8 to 11.0 mmol/L, is associated with an increased stroke risk in patients with coronary heart disease. Whether impaired glucose tolerance increases the risk of stroke in patients with transient ischemic attack ( TIA) or minor ischemic stroke is unknown. Methods - In total, 3127 patients with a TIA or minor ischemic stroke participated in the Dutch TIA Trial, testing 2 different doses of aspirin and atenolol versus placebo. We estimated the risk of stroke and the risk of myocardial infarction or cardiac death in relation to baseline nonfasting glucose levels ( mean 6.0, SD 2.2 mmol/L) with Cox proportional hazards regression analysis, adjusted for cardiovascular risk factors. Results - During 2.6 years follow-up, 272 patients ( 9%) experienced a stroke and 200 ( 6%) a myocardial infarction or cardiac death. We found a J-shaped relationship between baseline nonfasting glucose levels and stroke risk. Stroke risk was nearly doubled in patients with impaired glucose tolerance ( glucose 7.8 to 11.0 mmol/L) compared with those with normal glucose levels ( hazard ratio [ HR] 1.8, 95% CI, 1.1 to 3.0) and nearly tripled in diabetic patients ( glucose >= 11.1 mmol/L; HR 2.8, 95% CI, 1.9 to 4.1). Patients with low glucose levels ( < 4.6 mmol/L) had a 50% increased stroke risk ( HR 1.5, 95% CI, 1.0 to 2.2) compared with those with normal glucose levels. There was no association between glucose levels and risk of myocardial infarction or cardiac death. Conclusion - Impaired glucose tolerance is an independent risk factor for future stroke in nondiabetic patients with TIA or minor ischemic stroke.