Depressive symptoms that are present in midlife or in late life are associated with an increased risk of developing dementia, according to a report in the May issue of Archives of General Psychiatry, a JAMA Network publication.

Nearly 5.3 million individuals in the United States have Alzheimer disease (AD) and the resulting health care costs in 2010 were roughly $172 billion, the authors write as background information in the study. "Prevalence and costs of AD and other dementias are projected to rise dramatically during the next 40 years unless a prevention or a cure can be found. Therefore, it is critical to gain a greater understanding of the key risk factors and etiologic underpinnings of dementia from a population-based perspective," the authors write.

Deborah E. Barnes, Ph.D., M.P.H., of the University of California, San Francisco and the San Francisco Veterans Affairs Medical Center, and colleagues evaluated data from 13,535 long-term Kaiser Permanente members and examined depressive symptoms assessed in midlife (1964-1973) and in late life (1994-2000) and risks of developing dementia, Alzheimer disease (AD) and vascular dementia (VaD; dementia resulting from brain damage from impaired blood flow to the brain).

Depressive symptoms were present in 14.1 percent of study participants in midlife only, 9.2 percent in late life only and 4.2 percent in both. During six years of follow-up, 22.5 percent of patients were diagnosed with dementia; 5.5 percent with Alzheimer disease and 2.3 percent with VaD.

When examining AD and VaD separately, patients with late-life depressive symptoms had a two-fold increase in AD risk, and patients with midlife and late-life symptoms had more than a three-fold increase in VaD risk.

"Our findings suggest that chronic depression during the life course may be etiologically associated with an increased risk of dementia, particularly VaD, whereas depression that occurs for the first time in late life is likely to reflect a prodromal stage of dementia, in particular AD," the authors conclude.