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THURSDAY, Feb. 19 (HealthDay News) -- A rise in blood sugar levels causes poorer brain function in people with type 2 diabetes, according to a study that included nearly 3,000 people aged 55 and older at 52 sites in Canada and the United States.

The participants, who were part of a larger study on cardiovascular risk in diabetes, underwent cognitive tests designed to measure several aspects of memory function. The researchers found that a 1 percent increase in A1C levels (average blood glucose levels over a period of two to three months) was associated with slightly lower scores on tests of psychomotor speed, global cognitive function, memory and multi-tasking.

However, no link was found between tests scores and daily blood glucose levels, which are measured by a fasting plasma glucose test.

The findings appear in the February issue of Diabetes Care.

"One of the little-known complications of type 2 diabetes is memory decline leading to dementia, particularly Alzheimer's disease," principal investigator Dr. Jeff Williamson, of Wake Forest University Baptist Medical Center, said in a news release from the university.

"This study adds to the growing evidence that poorer blood glucose control is strongly associated with poorer memory function and that these associations can be detected well before a person develops severe memory loss," he said.

Previous research has shown that people with diabetes are 1.5 times more likely than those without diabetes to experience cognitive decline and develop dementia.

Williamson said that "people with type 2 diabetes and their health-care providers need to be careful in situations where there is education and teaching about diabetes care, as patients may need a little more time to absorb and process information."

And he urged people with diabetes to "be open to having a family member periodically making sure they are keeping track of managing their diabetes through monitoring, diet, exercise and medication."

More information

The U.S. National Diabetes Education Program has more about controlling diabetes.