Cognitive Impairment and Risk of Stroke: A Systematic Review and Meta-Analysis of Prospective Cohort Studies

BACKGROUND AND PURPOSE—Cognitive impairment is linked to vascular risk factors and brain vascular pathologies. Several studies have tested whether subjects with cognitive impairment have higher risk for stroke. The aim of this study was to systematically review available evidence on the association between cognitive impairment and risk of stroke to obtain precise effect estimates of the association and to identify which cognitive domains associate most with incident stroke. METHODS—PubMed, EMBASE, and Web of Science were searched from January 1, 1980, to October 1, 2013, without language restriction. Only prospective cohort studies were included. From each study, data on the association between cognitive impairment and stroke estimated with hazard ratios or relative risks with 95% confidence interval (CI) were extracted. For each study, risk of stroke per SD lower performance in various cognitive tests was calculated. RESULTS—Twelve studies were included, comprising 82 899 participants of whom 3043 had an incident stroke. The pooled relative risk per SD lower global cognitive performance was 1.19 (95% CI, 1.12–1.27). Each SD lower score in executive function or attention was associated with 1.14-fold (95% CI, 1.06–1.24) higher risk of stroke. Lower scores in memory were associated with 1.07-fold (95% CI, 1.02–1.12) higher risk of stroke, and lower scores in language were associated with 1.08-fold (95% CI, 1.02–1.16) higher risk of stroke. CONCLUSIONS—Cognitive impairment is associated with higher risk of stroke. The associations were not significantly different for executive function, memory, and language.