Dr. Joshua A. Sonnen of the University of Washington in Seattle and colleagues studied 196 individuals who were part of the Adult Changes in Thought Study, a community-based investigation of dementia.

After the participants died, autopsies were conducted on their brains and their cases were divided into four groups based on clinical information: those with diabetes and dementia, those with diabetes but no dementia, those with dementia but no diabetes and those without either disease.

In the 125 patients without dementia, neuropathological and biochemical factors did not differ based on diabetes status. However, the study, published in the Archives of Neurology, showed that among the 71 with dementia, two patterns of injury emerged based on whether the patients had diabetes and received diabetes treatment.

Those without diabetes had larger amounts of beta-amyloid buildup and greater free radical damage. Those with diabetes had more microvascular infarcts -- microscopic injury to small blood vessels in the brain known as arterioles -- and more inflammation in neural tissue.