Depression May Increase Risk of Later Dementia
Depression is commonly reported to co-exist in people with Alzheimer's disease, but a pair of studies published in the journal Neurology suggests that having depression at a younger age is a significant risk factor for later developing dementia.
Jane Saczynski PhD, associate professor of medicine at the University of Massachusetts Medical School, who led the first of the two studies, followed 949 elderly people for 17 years as part of the Framingham Heart Study. Twenty-two percent of those who had depression went on to develop dementia compared to 17% of those who did not have depression, representing a 70% increased risk.
The second study followed 1,239 people and found that the more times someone experienced depression, the higher their dementia risk was. Having two or more episodes of depression nearly doubled the risk of dementia.
The researchers stress that their studies do not prove cause and effect. Rebecca Wood, chief executive of the Alzheimer’s Research Trust, said, “Similarities in symptoms between dementia can mean the two are sometimes confused at the time of diagnosis, but we don’t know if they are biologically linked. These latest studies suggest that there may be profound connections between dementia and depression so we must expand the research to find more.”
Dr. Saczynski theorizes that brain chemistry, lifestyle factors such as diet and physical activity, and social engagement may play a role.
“Inflammation of brain tissue that occurs when a person is depressed might contribute to dementia,” she said. “Certain proteins found in the brain that increase with depression may also increase the risk of developing dementia.” In addition, depressed people tend to be less active and more withdrawn, habits that could influence the development of dementia.
The next step in this line of research is to examine brain images to see what roles depression and dementia may play in the brain, and better understand the mechanisms behind the connection between these two disorders, Saczynski said.