Longitudinal associations between late-life depression, cerebrovascular disease and cognition.

BACKGROUND: Depression and vascular disease can both be risk factors for cognitive decline. This study assessed whether indicators of vascular disease are associated with depression over time, and whether depression is associated with cognition independent of vascular disease.

METHODS: Participants were 1032 community-dwelling, older adults from the Sydney Memory and Ageing Study. Depressive symptoms were measured on the 15-item Geriatric Depression Scale, and depression trajectories were classified using latent class growth modelling. Global cognition and individual cognitive domains were assessed. Indicators of vascular disease were history of stroke or transient ischaemic attack (TIA) and total white matter hyperintensities (TWMH). Generalised linear mixed modelling assessed whether vascular markers were associated with change in depressive symptoms over time. Linear mixed modelling examined relationships between depression, vascular disease indicators, and cognition.

RESULTS: History of stroke/TIA or TWMH did not predict depression over time (p = 0.11 and p = 0.70). Baseline stroke/TIA history was associated with a decline in attention over time (b = -0.05, p = 0.04). Significant differences between latent depression trajectories classes in cognitive decline were observed, with participants who became depressed over time experiencing decline in global cognition (b = -0.04, p < 0.001), attention (b = -0.05, p < 0.001) and executive function (b = -0.05, p < 0.001), compared to the non-depressed group.

CONCLUSION: Our findings suggest that depression in later life may not precede cognitive decline. Instead, depressive symptoms and cognitive decline, particularly in attention and executive function, may evolve in tandem over time. This reinforces the importance of early identification and treatment of depression in older adults to potentially mitigate cognitive deterioration.