Association between mild cognitive impairment and APOE Ɛ4, low education level, and lack of spousal relationship in community-dwelling older persons in Nigeria

Background: Apolipoprotein Ɛ4 has been established as a risk factor for cognitive impairment and dementia among Caucasians; however, the relationship among Black Africans has not been consistent. Aims: This study aimed to determine the sex-related differences in mild cognitive impairment (MCI) and its association with apolipoprotein E (APOE) polymorphism and sociodemographic factors amongst community-dwelling older persons in Kano, Nigeria. Materials and Methods: One hundred and forty-three participants (males = 65 and females = 78) were randomly recruited. APOE was genotyped from peripherally extracted genomic DNA using the sequence-specific primer polymerase chain reaction with Hhal digestion. Cognition was assessed using the Montreal Cognitive Assessment Basic (MoCA-B). Data were analysed using the SPSS software. Results: The mean age of the participants was 65.69 years. The prevalence of MCI was 63.64%, and females were more affected (73.08% vs. 52.31%, χ 2 = 6.609; P = 0.010). The frequency of APOE genotypes was: E3/3-48%, E3/4-25.9%, E2/3-15.4%, E2/4 and E4/4-4.2%, and E2/2-2.8%, while its allelic distribution was: Ɛ3-68.2%, Ɛ4-19.2%, and Ɛ2-12.6%. Age and years of formal education were the independent predictors of the MoCA-B score. They explained 68% of the variance in MoCA-B score, while possession of at least one Ɛ4 allele (χ2 = 37.949, P < 0.001), low level of formal education (χ2 = 20.035, P = 0.001), being female (χ2 = 6.609, P = 0.010), being single (χ 2 = 6.303, P = 0.012), and having a lower monthly income (χ2 = 16.884, P = 0.001) were associated with MCI. Conclusions: The prevalence of MCI among older persons in Kano, Nigeria, is high and is associated with low levels of education, female sex, advanced age, low income, and APOE Ɛ4.