People who have symptoms of depression in middle age may be at increased risk of dementia decades later, a new study suggests.
The results, published in the May 2012 issue of the Archives of General Psychiatry, showed that those who had depression symptoms in the later stages of life were 70 percent more likely to develop dementia than those who didn't have symptoms during that time.
"Depression commonly occurs in individuals with cognitive impairment and dementia," the researchers wrote.
Although some studies have found that depression coincides with or follows the onset of dementia in older adults, most studies and several meta-analyses have concluded that depression precedes dementia and is associated with approximately a 2-fold increase in the risk of developing cognitive impairment or dementia.
The researchers evaluated more than 13,000 long term Kaiser Permanente members, looking for a history of depressive symptoms in midlife (1964-1973) and in late life (1994-2000), and compared the results with those suffering from Alzheimer disease and vascular dementia; dementia resulting from brain damage from reduced blood flow to the brain.
Depressive symptoms were present in 14.1 percent of subjects during their midlife, 9.2 percent in late life only, and 4.2 percent in both stages.
During the six years they had follow-ups, 22.5 percent were diagnosed with dementia.
About 5.5 percent were diagnosed with Alzheimer's disease, caused by protein deposits that stop brain function, and 2.3 percent were determined to have vascular dementia, which is caused by blood flow being blocked from the brain.
The chance of getting dementia increased by approximately 20 percent for those who had midlife depressive symptoms, 70 percent for those who had for late-life symptoms only, and 80 percent for those who exhibited the symptoms in both periods.
Depressive symptoms in mid and late stages showed double the risk from Alzheimer's, while the risk for vascular dementia increased threefold.
The researchers commented that future studies are necessary to determine if depression treatment during mid and late stages can help stave off dementia.
Given the anticipated increase in dementia prevalence during the next 40 years, even a small reduction in dementia risk would have a tremendous public health impact," they wrote.
SOURCE: D. E. Barnes, K. Yaffe, A. L. Byers, M. McCormick, C. Schaefer, R. A. Whitmer. Midlife vs Late-Life Depressive Symptoms and Risk of Dementia: Differential Effects for Alzheimer Disease and Vascular Dementia. Archives of General Psychiatry, 2012; 69 (5): 493 DOI: 10.1001/archgenpsychiatry.2011.1481