Depression in later life is associated with an increased risk of developing all forms of dementia, but in particular vascular dementia, according to the results of a new meta-analysis.

While previous studies have shown a link between depression and Alzheimer’s disease, the most common form of dementia, this meta-analysis is the first to show that late-life depression increases the risk of developing vascular dementia, and that risk is higher than for developing Alzheimer’s disease.

The study was conducted by researchers at the University of Pittsburgh School of Medicine and the Federal University of Minas Gerais School of Medicine and the results are published in the British Journal of Psychiatry.

Vascular dementia is the second most common form of dementia, and is associated with impaired judgment or ability to plan and complete tasks, as opposed to memory loss that is common in early stages of Alzheimer’s disease.

Meryl Butters, PhD, associate professor of Psychiatry at the University of Pittsburgh School of Medicine, and corresponding author of the study, said: “An understanding of how late-life depression increases the risk of dementia could lead to better prediction and prevention mechanisms. Early diagnosis and prevention of depression could have a major dual public health impact as they could also potentially prevent or delay cognitive decline and dementia in older adults.”

Late-life depression is one of the most common psychiatric illnesses in older adults, affecting 15% of adults aged over 65 in the United States – about 6 million people. Depression in late-life may be a relapse of an earlier depression, or it can be triggered by chronic illness – including degenerative brain diseases such as Alzheimer’s disease – grief, placement in a nursing home, or hospitalisation.

Late-life depression is associated with poorer general health and higher incidences of cardiovascular disease. Although the symptoms of depression vary, clinical depression is characterised by an inability to function normally or complete daily tasks, over a prolonged period of time.

The research evaluated a total of 23 community-based cohort studies as part of a meta-analysis to calculate the pooled risk of all forms of dementia, Alzheimer’s disease and vascular dementia in older adults with late-life depression. The findings concluded those with late-life depression are 1.85 times more likely to develop all forms dementia, but 2.52 times more likely to develop vascular dementia and 1.65 times more likely to develop Alzheimer’s disease.

The authors note that preventing depression and improving general health including cardiovascular health should be considered in public health policies associated with preventing and/or delaying the onset of dementia.

Dr Butters added: “Fortunately, we already know that depression can be prevented and treated. Now that we know the risks of dementia, we need to conduct clinical trials to investigate the impact of preventing depression on risk of cognitive decline and dementia in older adults.”

Reference: Diniz BS, Butters MA, Albert SM, Dew MA and Reynolds CF (2013) Late-life depression and risk of vascular dementia and Alzheimer’s disease: systematic review and meta-analysis of community-based cohort studies. British Journal of Psychiatry 202 329-335.