Apolipoprotein E Genotype, Vascular Risk and Early Cognitive Impairment in an African Caribbean Population

Abstract

A reduced risk of Alzheimer’s disease (AD) associated with the apolipoprotein E (APOE) Ε4 allele is reported in populations of African origin. In order to clarify possible reasons for this, we examined the association between APOE genotype and early cognitive impairment in a community-based African Caribbean UK population aged 55–75 years. APOE genotype was available for 202 participants, 57 (28%) of whom were classified as having relative cognitive impairment on a battery of neuropsychological tests. Cognitive impairment was negatively associated with Ε2 and positively but more weakly associated with Ε4. Effects of both alleles increased markedly after age 70. The effect of Ε4 was increased in combination with hypertension, diabetes or lower educational attainment, but these factors did not influence Ε2 effects. Cholesterol and triglyceride levels partially explained effects of Ε2, but did not account for those of Ε4. A reduced association between Ε4 and later AD in populations of African origin is unlikely to be explained by reduced cognitive effects or by differential mortality. However, it may be accounted for by vascular comorbidity. The different patterns of association between Ε2 and Ε4 alleles suggest different pathways of effect.