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

Depressive symptoms are common in mild cognitive impairment (MCI). These may be associated with poorer cognitive function and increased risks of dementia transition.

We aimed to examine the cognitive patterns associated with variations in depressive symptoms in neurodegenerative MCI without a primary mood disorder.

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.

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.

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.