Stroke and apolipoprotein E epsilon4 are independent risk factors for cognitive decline: A population-based study.

BACKGROUND AND PURPOSE Stroke and apolipoprotein E epsilon4 (ApoE epsilon4) are individually important risk factors for cognitive decline, including Alzheimer disease. It has been suggested that ApoE epsilon4 multiplies the risk for cognitive decline following stroke. In a population-based sample, using well-defined sensitive cognitive measures, this study investigates whether cognitive decline following stroke is worse for patients who carry the ApoE epsilon4 allele. METHODS Subjects were participants in the Longitudinal Aging Study Amsterdam (LASA). The sample consisted of 1224 subjects, aged 62 to 85 years, who participated in the 3-year follow-up examination and for whom ApoE and stroke data were complete. We assessed cognitive decline using the Mini-Mental State Examination, the Auditory Verbal Learning Test (memory: immediate and delayed recall), and the Coding Task (information processing speed). The effects of stroke and ApoE epsilon4 on cognitive decline were evaluated with ANOVA and multiple logistic regression analysis, adjusted for age, sex, education, and baseline cognition. RESULTS A synergistic effect modification for stroke and ApoE epsilon4 on cognitive decline was not observed. Unexpectedly, instead, stroke patients carrying the epsilon4 allele demonstrated a nonsignificantly lowered risk for Mini-Mental State Examination decline (OR=0.3; 95% CI 0.1 to 1.1). ApoE epsilon4 was associated with declines in information processing speed (OR=1.5; 95% CI 1.1 to 2.1) and small declines for immediate and delayed recall. CONCLUSIONS Stroke and ApoE epsilon4 may impair cognition through distinct nonsynergistic mechanisms. The slowing of information processing speed for ApoE epsilon4 carriers was more evident than impairment in memory.