Depression is a known risk factor for Alzheimer’s disease and other forms of dementia. Diabetes, too, has been linked to an increased Alzheimer’s risk. Now, a new study shows that having both diabetes and depression raises the risk of developing dementia even more.
The findings are important, since diabetes and depression are two of the most common ailments afflicting the elderly. Furthermore, both illnesses can be successfully treated or managed, which may help to ward off dementia and other complications.
Other studies have shown that having diabetes increases the risk of all kinds of dementia by 47 percent, and the risk of Alzheimer’s by 39 percent. Other reports estimate that having depression doubles the risk of developing Alzheimer’s or other forms of dementia.
The new report, part of the Diabetes and Aging Study, looked at more than 19,000 men and women of varying ethnicities who were part of a health care plan in Northern California. They ranged in age from 30 to 75. All had Type 2 diabetes, and 3,766, or nearly 20 percent, were also suffering from depression.
The study participants were followed for three to five years and given tests for memory problems and other signs of dementia. During that time, 238 developed dementia. Having depression along with diabetes resulted in a two-fold increase in risk of developing dementia, independent of other risk factors like smoking, cardiovascular disease, and obesity. A two-fold increase in risk translates to about a five-year earlier onset of Alzheimer’s symptoms, the researchers noted.
"Prior research has shown that both depression and diabetes are risk factors for dementia,” said study author Rachel Whitmer of Kaiser Permanente. “This study suggests that having both of these illnesses occurring together is associated with an even greater risk."
Particularly worrisome was that some of the younger people in the study, under age 65, were also at increased risk of dementia, which is uncommon in younger people. "Earlier onset of diabetes in patients with depression and greater risk of dementia in younger, compared to older patients, with depression and diabetes underscore the importance of evaluating the potential for early depression interventions to reduce the incidence of dementia," said lead author Dr. Wayne Katon, professor and vice chair of the University of Washington Department of Psychiatry and Behavioral Sciences.
It is important that anyone with diabetes and symptoms of depression be screened for the mental health disorder. Depression, of course, can make someone with diabetes less likely to comply with medications or to exercise regularly or watch their weight, all of which can worsen diabetes symptoms.
Other research suggests that effective treatment of depression and diabetes, as well as eating more fruits and vegetables, could potentially reduce dementia incidence by some 20 percent. Treatment of the depression may be particularly effective in reducing dementia risk.
"Since depression affects up to 20 percent of diabetic patients, it is critical to understand this relationship and further evaluate whether depression interventions have an impact on dementia risk in patients with diabetes," explained Andrew J. Karter, a co-author on the current report.
By ALZinfo.org, The Alzheimer's Information Site. Reviewed by William J. Netzer, Ph.D., Fisher Center for Alzheimer's Disease Research at The Rockefeller University.
Source: Wayne Katon, MD; Courtney R. Lyles, PhD; Melissa M. Parker, MS; et al:Association of Depression With Increased Risk of Dementia in Patients With Type 2 Diabetes: The Diabetes and Aging Study. Archives of General Psychiatry. Published online December 5, 2011. doi:10.1001/archgenpsychiatry.2011.154.