Background and purpose: High blood pressure is the most important risk factor for stroke. It is also known that diabetic patients are at increased risk of both hypertension and stroke. The aim of this study was to assess the independent effect of diabetes as a risk factor for stroke. Results from the previous studies of this question have been somewhat inconclusive.
Methods: We performed a prospective study (average follow-up, 16.4 years) of 8077 men and 8572 women who had participated in risk factor surveys in Eastern Finland in 1972 (20 years of follow-up) and 1977 (15 years of follow-up). Risk factors included in the current analyses were smoking, blood pressure, antihypertensive drug treatment, serum total cholesterol, and diabetes either at baseline or developed during the follow-up. Age- and risk factor-adjusted relative risks for death of stroke were determined with the Cox proportional hazards model.
Results: Diabetes mellitus was the strongest risk factor for death from stroke among both men and women in univariate and multivariate analyses. In addition, smoking and systolic blood pressure appeared to be independent risk factors among both sexes, as did serum total cholesterol among men. Men with diabetes at baseline appeared to be at a sixfold increased risk of death from stroke, while relative risk for men who developed diabetes during the follow-up was 1.7. In women, those who were diabetic at baseline were at higher risk of stroke than women who developed diabetes later (relative risks, 8.2 and 3.7, respectively). Of stroke deaths, 16% in men and 33% in women were attributed to diabetes.
Conclusions: Diabetic subjects have a very high risk of death from stroke, particularly women. Our data also suggest that the duration of diabetes is an important factor contributing to the risk of stroke.