Twenty percent of people older than 65 have diabetes, and many also think less clearly than they used to. Some studies have found a link between diabetes and cognitive impairment, but the link isn't clear, so researchers at Rush University Medical Center in Chicago tried to find out more.

What the researchers wanted to know: Does diabetes increase your risk of Alzheimer's or other cognitive decline?

What they did: Researchers used the Religious Orders Study, an ongoing study of 990 Catholic nuns, priests, and brothers over 55 who undergo annual testing and have agreed to donate their brains when they die. Each year, the subjects take tests to assess their memory, speed of perception, and visual and spatial ability. The researchers compared the risk of Alzheimer's among people with and without diabetes. Of the 824 people analyzed for this question, 127 had diabetes at some point during the study period.

What they found: People with diabetes had a 65 percent higher risk of developing Alzheimer's disease. For the measurements of cognitive decline, researchers found a difference between diabetics and nondiabetics only in the speed of making simple perceptual comparisons. Results were controlled for age, sex, and educational level.

What it means to you: If scientists can understand the link between diabetes and Alzheimer's, it might give more insight into the causes of Alzheimer's disease.

Caveats: A group of elderly Catholic priests, nuns, and brothers could hardly be considered representative of the general population.

Find out more: The Consortium to Establish a Registry for Alzheimer's Disease came up with the standards for diagnosing Alzheimer's. For information about Alzheimer's, go to the Alzheimer's Disease Education and Referral Center website.

Read the article: Arvanitakis, Z., Wilson, R.S., Bienias, J.L., Evans, D.A., and D.A. Bennett. "Diabetes Mellitus and Risk of Alzheimer Disease and Decline in Cognitive Function." Archives of Neurology. May 2004, Vol. 61, pp. 661–666.