APOE and diabetes mellitus: Controlling for sex, age, ethnicity, townsend deprivation index, assessment center, smoking status, alcohol use, APOE ε4 allele, hypertension, diabetes, CAD, and history of COVID-19 infection, a lower plasma Aβ42/40 ratio at baseline was significantly associated with a faster decline in memory performance, as measured by the paired associate learning test (β = −0.029, P = 0.019) (Fig. 1).