Racial Differences in Cognitive Function and Risk of Incident Stroke

Background and Purpose Cognitive impairment is associated with increased risk of stroke; however, it is not known whether this association varies by race. Our objective was to examine the association between cognitive function and the risk of stroke among non-Hispanic blacks and whites with no history of stroke. Methods Participants were from a population-based cohort study of 7205 older adults (61% black and 59% female) from Chicago's South Side. A standardized composite cognitive function score based on 3 components - global cognition (Mini-Mental State Examination), executive function (Symbol Digits Modalities test), and episodic memory (Delayed and Immediate Story Recall tests) - was used to predict risk of stroke (from Medicare hospitalization data) using a Cox model. Results During 72,868 person-years of follow-up, 16% (N = 1185) developed stroke. After adjusting for vascular risk factors, 1 standard deviation lower composite cognitive function score was associated with increased risk of stroke in blacks (hazard ratio [HR] = 1.76; 95% confidence interval [CI], 1.66-1.88), which was twofold higher than whites (HR = 1.38; 95% CI, 1.26-1.55) (P_difference =.002). Lower global cognition and executive function were associated with a similarly increased risk of stroke in blacks and whites. Lower episodic memory (composite of recall tests) was associated with increased risk of stroke that was twofold higher in blacks (HR = 1.12; 95% CI, 1.10-1.14) than in whites (HR = 1.06; 95% CI, 1.04-1.09). Conclusions Lower cognitive function was associated with increased risk of stroke and this association was stronger among blacks than whites. Future studies are needed to determine factors that can explain this finding.