Cross-sectional and longitudinal associations between depressive symptoms and cognitive performance in mild cognitive impairment.

Abstract

BACKGROUND: Depressive symptoms are common in mild cognitive impairment (MCI). These may be associated with poorer cognitive function and increased risks of dementia transition. AIMS: We aimed to examine the cognitive patterns associated with variations in depressive symptoms in neurodegenerative MCI without a primary mood disorder. METHOD: Individuals with MCI (n = 123), including MCI due to Alzheimer's disease (n = 54) and MCI with Lewy bodies (n = 69), underwent repeated annual assessment of cognitive function and concurrent depressive symptoms using the Addenbrooke's Cognitive Examination-Revised and the Geriatric Depression Scale-15, respectively.Between- and within-person differences in depressive symptoms were disaggregated and related to between- and within-person cognitive differences and modification of cognitive performance trajectories over time. RESULTS: There was strong evidence of a state-based association between depressive symptoms and cognitive function. Intra-individual differences in depressive symptoms were negatively associated with concurrent cognitive performance such that a 2-point increase in depressive score explained a 1-point decrease in cognitive score, on average (point estimate -0.56, 95% credibile interval (CrI) -1.05 to -0.08).The data did not support a trait-based association between depressive symptoms and cognitive performance (point estimate 0.10, 95% CrI -0.42 to 0.59), nor any between- or within-person trajectory modification associated with depressive symptoms. CONCLUSIONS: Within-person variations in depressive symptom severity are associated with acute cognitive performance differences. Cognitive scores derived during active depressive periods may underestimate longer-term cognitive capabilities. Treating depressive symptoms in MCI may clarify underlying cognitive performance capacity, and help maintain optimal cognitive function for longer.