Diabetes Mellitus: A Risk Factor for Ischemic Stroke in a Large Biracial Population

Background and Purpose— We previously reported increased incidence of ischemic stroke among both blacks and whites with diabetes mellitus, especially in those aged <55 years. With rising prevalence of diabetes mellitus in the past decade, we revisit the impact of diabetes mellitus on stroke incidence in the same population (≈1.3 million) 5 and 10 years later. Methods— This is a population-based study. First ischemic strokes among black and white residents of the 5-county Greater Cincinnati/Northern Kentucky region, aged ≥20 years, for periods 7/1993 to 6/1994, 1999, and 2005, were included in this analysis. Incidence rates were adjusted for sex, race, and age, as appropriate, to the 2000 US population. Results— History of diabetes mellitus among first ischemic strokes was reported for 493/1709 (28%) in 1993/1994, 522/1778 (29%) in 1999, and 544/1680 (33%) in 2005. Risk ratios (95% confidence interval) for rates of stroke in those with versus without diabetes mellitus for blacks reduced significantly from 5.6 in 1993/1994 to 3.2 in 2005; for whites the risk ratio remained stable at 3.8 in 1993/1994 and 2005. However, risk ratios varied with age, with an overall 5- to 14-fold increased risk observed in those aged 20 to 65 years. Conclusions— Those with diabetes mellitus remain at greatly increased risk for stroke at all ages, especially <65 years, regardless of race. The rates and risk ratios for 1999 and 2005, although similar to those previously reported for the mid-1990s, take on increased significance, given the epidemic of diabetes mellitus and metabolic syndrome throughout the US and the world.