Apolipoprotein E and Change in Episodic Memory in Blacks and Whites

Abstract

Background: Apolipoprotein E (APOE) ε4 is related to faster decline in episodic memory in Whites, but the relation is unknown in Blacks. The purpose of this study was to determine whether ε4 has a selective effect on decline in episodic memory in Blacks. Methods: Data are from two cohort studies with similar design. The sample consisted of 1,211 participants [28.4% Blacks, mean age = 78.6 years (SD = 7.4), education = 14.7 years (SD = 3.1)] without dementia at baseline, who underwent annual clinical evaluations for up to 6 years. Summary measures of 5 cognitive abilities were derived from 18 neuropsychological tests. Results: In mixed models that controlled for age, sex, education, and race, possession of ε4 (present in 32.9% of Blacks and 21.0% of Whites, p < 0.001) was related to faster decline in episodic memory and 4 other cognitive abilities (all p values <0.01). In separate models that examined the interaction of race and ε4 on decline, there was no significant difference between Blacks and Whites in the effect of ε4 on decline in episodic memory, perceptual speed, or visuospatial ability. By contrast, the effect of ε4 differed for semantic memory and working memory. Results were similar after adjusting for vascular conditions. Conclusions: The results suggest that APOE ε4 is related to a faster rate of decline in episodic memory in Blacks similar to Whites. In addition, there were racial differences in the effect of ε4 in other cognitive abilities such that the ε4 allele was related to faster decline in semantic memory and working memory for Whites but not for Blacks.