People with diabetes appear to be at a significantly increased risk of developing dementia, according to a study published in the September 20, 2011, print issue of Neurology®, the medical journal of the American Academy of Neurology.

"Our findings emphasize the need to consider diabetes as a potential risk factor for dementia," said study author Yutaka Kiyohara, M.D., Ph.D., of Kyushu University in Fukuoka, Japan. "Diabetes is a common disorder, and the number of people with it has been growing in recent years all over the world. Controlling diabetes is now more important than ever."

People with diabetes were more likely to develop Alzheimer's disease and other types of dementia, such as vascular dementia, which occurs when there is damage to blood vessels that eventually deprive the brain of oxygen.

For the study, a total of 1,017 people who were age 60 and older were given a glucose tolerance test after an overnight fast to determine if they had diabetes. Study participants were monitored for an average of 11 years and then tested for dementia. During the study, 232 people developed dementia.

The study found that people with diabetes were twice as likely to develop dementia as people with normal blood sugar levels. Of the 150 people with diabetes, 41 developed dementia, compared to 115 of the 559 people without diabetes who developed dementia.

The results remained the same after the researchers accounted for factors such as high blood pressure, high cholesterol and smoking. The risk of dementia was also higher in people who did not have diabetes, but had impaired glucose tolerance, or were "pre-diabetes."

In addition, the study found the risk of developing dementia significantly increased when blood sugar was still high two hours after a meal.

This study was supported by the Japanese Ministry of Education, Culture, Sports, Science and Technology and the Ministry of Health, Labor and Welfare.