High blood sugar may affect memory in some people

Nanci Hellmich | USA TODAY

People who didn't have type 2 diabetes but had blood sugar at the high end of the normal range performed worse on memory tests than those with lower blood sugar, a study out Wednesday shows.

Researchers in Germany recruited 141 people, average age 63, who did not have type 2 diabetes or prediabetes, and they showed no signs of memory problems. The study participants took a series of memory tests and had their blood sugar tested. They also had brain scans to measure the size of the hippocampus area, which plays an important role in memory.

Researcher Agnes Flöel of Charité University Medicine in Berlin says she and her colleagues "correlated long-term blood-sugar levels with the number of words people could recall on a memory test." She says they found that higher long-term blood-sugar levels went along with being able to recall fewer words.

"We also found that people with higher blood-sugar levels had smaller volumes in the size of their hippocampus," she says.

Flöel says the findings, reported in the medical journal Neurology, published by the American Academy of Neurology, suggest that even for people within the normal range of blood sugar, lowering their levels might be a possible way to prevent memory problems as they age.

She points out that the study is relatively small and doesn't prove cause and effect. There's a need for large clinical trials to test whether lowering glucose will help with the prevention of dementia, she says.

Robert Ratner, the chief scientific and medical officer for the American Diabetes Association, says it's important to realize that this study shows an "association. They are looking at a single glucose level in time and memory. They haven't shown that the memory loss is either due to the higher glucose level, or that lowering glucose would improve memory."

Still, he says, "it's not surprising that glucose levels can potentially have these kinds of negative impacts. The risk of dementia is higher in people with diabetes.

"It has been well established that elevated glucose impacts brain function and recovery in people following a stroke," he says.

When something goes wrong with the body's ability to regulate glucose levels in the blood, the brain is not able work as well as it should, says Keith Fargo of the Alzheimer's Association.

If glucose is not functioning properly, it can affect brain function and brain health over the long-term, says Rachel Whitmer, a senior research scientist at Kaiser Permanente Division of Research. "This study adds to the literature that what's good for the heart is what's good for the brain."

Her research shows that people with type 2 diabetes who have poor blood-sugar control are at a greater risk of dementia. "Elderly people with type 2 diabetes are almost twice as likely to develop dementia."

So how hard is it to lower your blood sugar if you are in the normal range?

Your glucose level is determined by a combination of "genetics, diet and hormonal response," Ratner says. "For those who have perfectly normal glucose metabolism, there is little they can do to change their level. The body controls glucose very tightly. The body is that good."

If you want to keep your blood sugar in a healthy range, that doesn't mean "you should never eat sugar," he says. It means you should eat a healthy diet with a reasonable number of calories and a balanced intake of protein, fat and carbohydrates, he says.

And physical activity is important, because it improves the body's ability to utilize insulin, so a regular exercise program makes a person more insulin-sensitive — their body responds to the insulin they make more effectively, he says.

Adds Whitmer: "We know people who live an active lifestyle and eat a healthy diet are less likely to get type 2 diabetes and dementia. Having a healthy lifestyle is good for the brain."