Does Depression Contribute to Dementia?
The World Health Organization estimates that 47.5 million people worldwide have dementia. This number is projected to increase to nearly 76 million by 2030. Lacking a cure, researchers have put a focus on preventing or delaying the onset of dementia. Numerous studies have found an association between depression and Alzheimer’s disease; several studies have also looked at the relationship between depression and vascular dementia.
Researchers at the University Of Pittsburgh School Of Medicine and the Federal University of Minas Gerais School of Medicine reviewed 23 of these studies to determine if late-life depression increases the risk of Alzheimer’s and vascular dementia. Their findings were published in the British Journal of Psychiatry.
The Difference Between Alzheimer’s and Vascular Dementia
Alzheimer’s disease, by far, is the leading cause of dementia, contributing to 60-70 percent of dementia cases. In its early stages, Alzheimer’s is marked by memory loss and apathy. In the latter stages, individuals living with Alzheimer’s become disorientated, agitated and eventually lose their mobility and ability to speak.
Vascular dementia, the second most common type, is caused by a decrease of blood supply to the brain. This may be caused by a stroke, or a narrowing of small blood vessels in the brain as the diseased vessels thicken and become stiff. This type of dementia is associated with impaired judgment and inability to plan or complete tasks.
Depression in Later Life Increases Dementia Risk
Late-life depression, according to the study authors, affects 15 percent of older adults (age 65 or older) in the United States. It may be a relapse of an earlier depressive episode or may be triggered by physical and social changes that occur with aging. Previous research associates late-life depression with poor overall health and cardiovascular disease. The University Of Pittsburgh study found that individuals with late-life depression are two-and-a-half times more likely to develop vascular dementia. Late-life depression also poses a 65 percent increased risk of Alzheimer’s disease.
Depression, including late-life depression, is treatable. These findings suggest strategies to prevent and treat depression may have a significant impact on public health. Noting the association between depression and cardiovascular disease, the study authors suggest public policies aimed at improving general and cardiovascular health could delay or prevent dementia in older adults. “Fortunately, we already know that depression can be prevented and treated,” says co-author Meryl Butters. “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.”