Depression course predicts dementia risk

By Lucy Piper

Patients with late-life depression have an increased risk of dementia if their symptoms increase over time, whereas a single episode of depression, even if severe, does not carry a significant risk, study findings indicate.

Studying trajectories of depression is likely to be a more accurate way of distinguishing patients at risk of dementia than single assessments, say M Arfan Ikram (Erasmus University Medical Center, Rotterdam, the Netherlands) and colleagues.

They studied five trajectories of depression characterised by low, decreasing, remitting, increasing or high Centre for Epidemiology Depression Scale scores in 3325 individuals aged 55 years or older participating in the Rotterdam Study.

The 255 individuals whose depressive symptoms started low and steadily increased over an 11 year-period had a 42% increased risk of dementia and a 44% increased risk of Alzheimer's disease in the subsequent 10 years compared with the2441 individuals whose depressive symptoms started and remained low.

Follow-up was 26,330 person-years and 434 participants developed incident dementia, including 348 with Alzheimer's disease.

Only an increasing course of depression, most notably after the first 3 years, was significantly associated with an increased risk of dementia; there were no significant associations for the remaining trajectories of moderately high starting scores that remitted (n=369); low starting scores that increased and then remitted (n=170) or high starting scores that were maintained (n=90).

"This finding is consistent with the prodromal hypothesis, which suggests that depressive symptoms in older age possibly represent a prodrome or an early stage of dementia", the researchers suggest.

"Indeed, depressive symptoms might appear as a reaction to underlying subclinical cognitive impairment, and lie in a continuum between subclinical cognitive impairment and overt dementia."

The researchers also note in The Lancet Psychiatry that the increasing depression course was associated with a 58% increased risk of dementia after censoring for incident stroke and a 45% increased risk after accounting for mortality as a competing risk.

In a related Comment, Simone Reppermund (University of New South Wales, Sydney, Australia) says that the study answers the question of whether depression modifies the risk of dementia, but the question of how remains.

"More studies of depression trajectories over a long period, with inclusion of biological measures, are necessary to understand the link between depression and dementia, in particular the underlying mechanisms", she writes.

"A focus on lifestyle factors such as physical activity and social networks, and biological risk factors such as vascular disease, neuroinflammation, high concentrations of stress hormones, and neuropathological changes, might bring new treatment and prevention strategies a step closer."

Licensed from medwireNews with permission from Springer Healthcare Ltd. ©Springer Healthcare Ltd. All rights reserved. Neither of these parties endorse or recommend any commercial products, services, or equipment.