NEW YORK (Reuters Health) - Older adults with type 2 diabetes may have a steeper mental decline as they age, a large study suggests.
Diabetes is known to raise the risk of a number of major health problems, including heart disease and kidney failure. More recently, studies have also linked diabetes to speedier mental decline and dementia in older adults.
These latest findings, published in the Journal of the American Geriatric Society, confirm those earlier reports -- and suggest that the longer a person has had diabetes, the more substantial the cognitive decline over time.
For the study, researchers led by Dr. Olivia Okereke, of Harvard Medical School in Boston, examined data from the Physicians' Health Study and the Women's Health Study -- two long-term projects looking at the health of thousands of U.S. men and women.
The researchers looked at the association between diabetes and late-life cognitive impairment in 5,907 men and 6,326 women. Participants were in their early 70s, on average, when they were first assessed for memory, thinking and other cognitive abilities; they were tested again roughly two years later, and women had a third test around the four-year mark.
In general, Okereke and her colleagues found, men and women with diabetes performed more poorly on the initial cognitive tests, then showed a more marked decline on subsequent tests.
In addition, participants with longer-standing diabetes tended to be in worse cognitive shape at the outset, and show a steeper decline over time.
There are several plausible reasons why diabetes might fuel age-related mental decline, according to the researchers.
One is that diabetes can damage the blood vessels that supply the brain, diminishing blood flow and thereby contributing to cognitive problems.
In addition, people with diabetes typically have chronically high levels of the blood-sugar-regulating hormone insulin. And some research suggests that elevated insulin concentrations may boost the body's levels of amyloid-beta protein, which build up to form the "plaques" seen in the brains of people with Alzheimer's disease.
More studies are now needed to find out precisely how diabetes affects older adults' mental function, Okereke and her colleagues conclude.
SOURCE: Journal of the American Geriatrics Society, June 2008.