Depression and Cognitive Function in Mild Cognitive Impairment: A 1-Year Follow-Up Study

The coexistence of depression with mild cognitive impairment (MCI) seems to increase the risk of dementia. However, the explanations of that relationship have been inconsistent. We investigated cognitive profiles in patients with MCI with and without depression and whether changes in depression symptoms affect cognition longitudinally.For the study, 161 patients with MCI were divided into a depressed group (D+) and a nondepressed group (D-). After 1 year, we redivided the original D- group into D- and newly developed depression (Dd) groups and the D+ group into improved depression (Di) and nonimproved depression (Dn) groups. Neuropsychological tests assessing depression and cognitive domains were performed at baseline and follow-up.When age-adjusted, the D+ group showed significantly poorer performance in general cognition and some subtests regarding memory, executive function, and attention. At the 1-year follow-up, changes in the calculation test ( P = .005) and Controlled Oral Word Test (COWAT; P = .048) were significantly different between groups. Only the Di group showed significant improvement in calculation. The Dn group showed significant decrement in COWAT that was significantly different from that of the Di group, which showed no significant change.Patients with depression having MCI showed poorer cognitive function than nondepressed patients with MCI in some cognitive domains. Improvement in depression was related to improvement or prevention of decline in cognitive measures.