Higher blood sugar tied to memory problems: study

By Andrew M. Seaman

Higher blood sugar levels shy of diabetes or even pre-diabetes levels was associated with lower memory and brain changes in a new cross-sectional study from Germany.

"Our results indicate that even in the absence of manifest type 2 diabetes mellitus or impaired glucose tolerance, chronically higher blood glucose levels exert a negative influence on cognition, possibly mediated by structural changes in learning-relevant brain areas," the researchers say.

Previous studies had found links between diabetes and impaired glucose intolerance and poor brain function and dementia, lead author Dr. Agnes Flöel told Reuters Health.

"We were also interested if this extends to people who are still in the normal range," Flöel, a neurologist at Charité University Medicine in Berlin, said.

For the new study, Flöel and her colleagues recruited 141 people from Berlin. None of them had diabetes or memory problems.

Memory was tested using the Rey Auditory Verbal Learning Test. Peripheral levels of fasting HbA1c, glucose, and insulin and MRI scans were acquired to assess hippocampal volume and microstructure.

"Lower HbA1c and glucose levels were significantly associated with better scores in delayed recall, learning ability, and memory consolidation. In multiple regression models, HbA1c remained strongly associated with memory performance," they reported online October 23 in Neurology.

Overall, people with higher blood sugar readings performed worse on the memory test, compared to those with lower blood sugar levels, the researchers say.

Even within normal HbA1c ranges, an increase of about 7 units on that blood test was tied to participants being able to remember two fewer words after 30 minutes on the memory test, they found.

That difference, however, would not be noticeable between two people, according to Dr. Antonio Convit, who was not involved in the new study but has done similar research.

"We've known about this for a little while," Convit, of the New York State Office of Mental Health's Nathan Kline Research Institute, said.

Another finding in line with past research, Convit said, was that MRIs showed the hippocampus, the brain's memory center, was smaller among people with higher blood sugar levels.

But the new study can't say blood sugar levels caused the memory problems or smaller brains, Flöel and her colleagues say.

For example, the researchers may not have been able to account for the effects of memory loss due to aging, Convit said.

"One thing that could be concluded from this is being fitter and keeping a good check on your weight may be useful if you want to keep your brain working properly," he said.

And for those people who already have blood sugar levels on the low end of the healthy range, Flöel said eating well and getting plenty of exercise "will at least be good for your heart - if not for your brain."

SOURCE: http://bit.ly/HhuXuN

Neurology 2013.