APOE E4 is associated with cognitive decline but not with disease risk or age of onset in Nigerians with Parkinson’s disease

Abstract The relationship between APOE polymorphisms and Parkinson’s disease (PD) in black Africans has not been previously investigated. We evaluated the association between APOE polymorphic variability and cognition in 1100 Nigerians with PD and 1097 matched healthy controls. Cognition in PD was assessed using the single item cognition question (item 1.1) of the MDS-UPDRS. APOE genotype and allele frequencies did not differ between PD and controls (p > 0.05). No allelic or genotypic association was observed between APOE and age at onset of PD. In PD, APOE ε4/ε4 conferred a two-fold risk of cognitive impairment compared to one or no ε4 (HR: 2.09 (95%CI: 1.13–3.89; p = 0.02)), while APOE ε2 was associated with modest protection against cognitive impairment (HR: 0.41 (95%CI 0.19–0.99, p = 0.02)). Altogether, our findings support previous studies in other ancestries, implying a role for APOE ε4 and ε2 as risk and protective factors respectively for cognitive decline in PD.