The results of an analysis of more than 50,000 people in 23 different population studies indicates that depression later in life is associated with an increased risk for dementia and Alzheimer's disease.
Analysis of the studies also indicates that there is a significant risk of vascular dementia (stroke-based dementia), in older adults who have "late-life depression." According to the authors of the study, late-life depression is extremely common among older adults. The occurrence of that depression has been found to be highly reoccurring, difficult to treat and chronic, significantly affecting an individual's ability to function.
The study, published in the May 2013 issue of the British Journal of Psychiatry, shows a strong association between depression and developing Alzheimer's disease. Researchers stated that they believe one or more depressive episodes can increase someone's risk for dementia syndromes such as vascular dementia as well as Alzheimer's disease. Connecting the two may help researchers help develop proactive preventative measures as well as long-term predictive models for patients.
Researchers also stated that the prevention of even a fraction of the number of cases of depression might reduce the development of Alzheimer's disease in the tens of thousands. They also stressed that the risk for vascular dementia appeared to be much higher than the risk for Alzheimer's disease in the individuals who were late-life depressed.
The study looked at 23 different cohort studies which followed patients 50 and older who did not display any signs of dementia during baseline testing. The studies followed up every five years for dementia and Alzheimer's disease, vascular dementia studies were followed at six-year intervals. Depression was scored on a ratings scale without structured interviews.
Though it is not definitive that late-life depression is a cause of dementia, says paper co-author Meryl Butters, associate professor of psychiatry at the University Of Pittsburgh School Of Medicine, it seems likely to contribute to it. Current theory holds that depression can cause minor brain damage, which can lead to the degenerative process of dementia.
The study authors stated that public health policies which focus on the prevention or delay of dementia in older adults should focus on working to prevent depression and healthy behaviors which reduce cardiovascular risk factors. They also urged for clinical trials which would look at how preventing depression in older adults lowers the risk of cognitive impairment and dementia later.
A large body of research has amassed which also links late-life depression to increased health risks, social isolation and an increased risk of death.