Cognitive Variability, Brain Aging, and Cognitive Decline in Late-Life Major Depression.

Objectives Older adults with late-life major depression (LLMD) are at increased risk of dementia. Dispersion, or within-person performance variability across cognitive tests, is a potential marker of cognitive decline. This study examined group differences in dispersion between LLMD and non-depressed healthy controls (HC) and investigated whether dispersion was a predictor of cognitive performance one year later in LLMD. We also explored demographic, clinical, and structural imaging correlates of dispersion in LLMD and HC. We hypothesized that dispersion would be greater in LLMD compared with HC and would be associated with worse cognitive performance one year later in LLMD. Design Participants were enrolled in the Neurobiology of Late-Life Depression (NBOLD), a naturalistic longitudinal investigation of the predictors of poor illness course in LLMD. Participants The baseline sample consisted of 121 older adults with LLMD and 39 HC; of these subjects, 94 LLMD and 35 HC underwent MRI. One-year cognitive data was available for 107 LLMD patients. Measurements All participants underwent detailed clinical and structural MRI at baseline. LLMD participants also completed a comprehensive cognitive evaluation one year later. Results Higher test dispersion was evident in LLMD when compared with non-depressed controls. Greater baseline dispersion predicted one-year cognitive decline in LLMD patients even when controlling for baseline cognitive functioning and demographic and clinical confounders. Dispersion was correlated with white matter lesions in LLMD but not HC. Dispersion was also correlated with anxiety in both LLMD and HC. Conclusions Dispersion is a marker of neurocognitive integrity that requires further exploration in LLMD. This article is protected by copyright. All rights reserved.