Previous studies have shown an association between depression and Alzheimer's disease, but this is the first meta-analysis that specifically addresses the risk of Alzheimer's disease and vascular dementia in older adults with late-life depression. The study, conducted by researchers at the University of Pittsburgh School of Medicine and the Federal University of Minas Gerais School of Medicine, is also the first to show that late-life depression increases the risk of vascular dementia and that the risk of vascular dementia is greater than the risk of Alzheimer's disease for older adults with depression.
"All-cause dementia" refers to all dementia syndromes, the most common of which is Alzheimer's disease, accounting for 60 to 80 percent of all dementia cases. Alzheimer's disease is associated with memory problems and apathy in early stages, and impaired judgment, confusion, disorientation, behavior changes, and difficulty speaking in later stages. Vascular dementia is the second most common cause 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.
"An understanding of how late-life depression increases the risk of dementia could lead to better prediction and prevention mechanisms," said Meryl Butters, Ph.D., associate professor of Psychiatry at the University of Pittsburgh School of Medicine, and corresponding author of the study. "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 percent of adults aged 65+ in the United States, or approximately 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 hospitalization. Late-life depression is associated with poorer general health and higher incidences of cardiovascular disease.
Although the symptoms of depression vary, clinical depression is characterized 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-cause 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-cause dementia
- 1.65 times more likely to develop Alzheimer's disease
- 2.52 times more likely to develop vascular dementia
"Fortunately, we already know that depression can be prevented and treated," added Dr. 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."
This research was sponsored by the National Institute of Mental Health (NIMH) and the John A. Hartford Foundation Center of Excellence in Geriatric Psychiatry at UPMC.