APOE and Cognitive impairment: In APOE ε4 carriers, low serum high-density lipoprotein was positively associated with cognitive impairment (Wald’s χ2 = 8.200, df = 1, OR = 60.335, p = 0.004) and serum high-density lipoprotein levels were positively correlated with Mini-Mental State Examination score (r = 0.217, df = 176, p = 0.004).