Association of depression and diabetes mellitus with processing speed, inhibitory control and cognitive flexibility in older adults with mild cognitive impairment

Abstract

AbstractBackgroundDepression and diabetes mellitus (DM) are associated with an increased risk for dementia and mild cognitive impairment (MCI). Subcortical anatomical changes associated with processing speed impairment are shared by both DM subtypes. This profile is similar for depression, a condition in which processing speed and executive functions mediate deficits in other domains. Thus, the aim of this work is to investigate the interaction between diabetes and depression with executive functions and processing speed on older adults with mild cognitive impairment.Method76 elderly people aged 60 to 96 years (M=75, SD=7.5) from UFMG outpatient clinic for older adults on Instituto Jenny de Andrade Faria participated in the study, predominantly low formal education (M=4, SD=4.5), 23 with significative depressive symptoms, 21 with diabetes mellitus, and 7 with both conditions. Multivariate analysis of variance was used (with cognitive variables as dependent, depression and diabetes as factors and age and education as covariates). Statistical method used was GLM and post‐hoc LSD analysis (Fisher's least significant difference). The level of significance adopted was 0.05. Processing speed, inhibitory control and cognitive flexibility were the study dependent variables, measured by the Five Digit Test.ResultDiabetes is associated with processing speed impairment (F =5,505; p =0,022; partial η2 = 0,073) and depression symptoms with decrease in inhibitory control (F =6,467; p =0,013; partial η2 = 0,085). The interaction between two conditions is associated with poorer performance in inhibitory control (F =6,423; p =0,014; partial η2 = 0,084).ConclusionSubcortical anatomical changes associated with processing speed impairment are shared by depression and diabetes mellitus. But when two conditions are compared on a similar group of older adults with mild cognitive impairment, executive functions decline is more expressive than processing speed on patients with depression. These results corroborate those found in the literature, where the cognitive decline in patients with depression is mediated by executive functions and on diabetes by processing speed.