When blood sugar levels rise in people with type 2 diabetes, they stop thinking as well, according to new research from the Wake Forest University Baptist Medical Center.

A drop in test scores was seen when people had high blood glucose levels over two to three months, but the drop was not seen because of changes in blood sugar through the day.

The results were based on studies of nearly 3,000 people over the age of 55.

"One of the little-known complications of type 2 diabetes is memory decline leading to dementia, particularly Alzheimer's dementia," said Dr. Jeff Williamson. "This study adds to the growing evidence that poorer blood glucose control is strongly associated with poorer memory function."

Others studies have found that people with diabetes are 50 percent more likely to get Alzheimer's disease than other people, according to a news release. Chronic exposure to high blood sugar may be to blame.

The study appeared in the journal Diabetes Care.