Depressive symptoms that occur in both midlife and late life are associated with an increased risk of developing vascular dementia, while symptoms that occur in late life only are more likely to be early signs of Alzheimer's disease, according to University of California at San Francisco and Kaiser Permanente researchers.
The study, which appears in the current issue of the Archives of General Psychiatry, is the first to examine whether midlife or late-life depression is more likely to lead to either Alzheimer's disease or vascular dementia in the long term. The researchers explain that vascular dementia, the second most common type of dementia, develops when impaired blood flow to parts of the brain deprives cells of nutrients and oxygen.
"People who had depressive symptoms in both midlife and late life were much more likely to develop vascular dementia, while those who had depressive symptoms in late life only were more likely to develop Alzheimer's disease," said the study's lead author Deborah E. Barnes, PhD, MPH, with the UCSF Departments of Psychiatry and Epidemiology & Biostatistics and the San Francisco Veterans Affairs Medical Center.
"The findings have important public health implications because they raise hope that adequate treatment of depression in midlife may reduce dementia risk, particularly vascular dementia, later in life," added Rachel Whitmer, PhD, a research scientist at the Kaiser Permanente Northern California Division of Research and the principal investigator of the study.
UCSF and Kaiser Permanente investigators examined the association between depressive symptoms and dementia over the course of 45 years in a longitudinal study of more than 13,000 long-term members of the Kaiser Permanente Northern California integrated care delivery system. The study population consisted of members who participated in a voluntary health examination called the Multiphasic Health Checkup in San Francisco and Oakland during 1964-1973 when they were 40-55 years old.
Participants were evaluated for depressive symptoms in midlife as part of the Multiphasic Health Checkup and again in late life between 1994-2000. Between 2003-2009, 3,129 participants were diagnosed with dementia.
Though more research is needed, the findings suggest that depression that begins in late life may be an early symptom of Alzheimer's disease, while chronic depression over the life course may reflect a long-term process of changes to blood flow in the brain associated with increased risk of vascular dementia.
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Arch Gen Psychiatry. 2012;69:493-498.