Diabetes mellitus as a risk factor for stroke.

To evaluate the relative potency of diabetes mellitus as a risk factor for stroke, the relative frequency of stroke symptoms was compared among cohorts with and without diabetes. Stroke symptoms were classified as atherothrombotic cerebral infarctions, transient ischemic attacks, reversible ischemic neurologic deficits, and multi-infarct dementia. The groups were compared according to the occurrence of these symptoms, and both cross-sectional and longitudinal designs were used to study 293 consecutive patients referred to this laboratory and to contrast groups with and without diabetes. Hypertension, heart disease, and stroke symptoms and signs were more frequent among diabetics than among age-matched nondiabetics. Among diabetics, strokes occurred at an earlier age and were more common among men. Regression analyses assigned diabetes second to hypertension as a risk factor for stroke, followed by heart disease and smoking. Diabetes associated with hypertension or hyperlipidemia added significantly to stroke risk. Initially, cerebral blood flow values and cognitive test scores were equivalent among diabetics and nondiabetics; after 3 years, cognition became significantly impaired among diabetics, despite better maintenance of cerebral blood flow among treated diabetics compared with nondiabetics. Diabetes acts to compound risk for stroke not only by promoting cerebral atherogenesis but also by aggravating other risk factors including hypertension, heart disease, and hyperlipidemia.