Diabetes slows some aspects of mental function

By Anne Harding

NEW YORK (Reuters Health) - Type 2 diabetes may put the brakes on people's ability to process certain types of information quickly and precisely, according to a new study investigating how the illness affects brain power.

Dr. Roger Dixon of the University of Alberta in Edmonton, Canada and his colleagues found small but significant differences between people with diabetes and their healthy peers on some tests of brain function and speed.

"The deficits we observed in this study are not likely to adversely affect most older diabetes patients' everyday life activities," Dixon told Reuters Health. "However, the cognitive slowing we observed could indicate the 'leading edge' of progressive and broader cognitive decline occurring with diabetes in late life. In a three-year follow-up to these patients, we found the present effects continued, deepened, and broadened."

Dixon's team had 465 men and women between 55 and 81 years old, 41 of whom had diabetes, complete several tests of memory, learning and executive function.

While people with type 2 diabetes did just as well as their healthier peers on tests of memory, fluency, reaction time, and perceptual speed, they fared worse on some tests of executive functioning. Specifically, they weren't as quick on a task that required them to complete a sentence with a single word or provide a word that didn't complete the sentence properly. They also took longer on a test that required them to read a string of letters and state whether the letters spelled an English word, and another test requiring them to read sentences and say whether or not they were "plausible or nonsensical."

It's not clear how diabetes might influence brain function, Dixon said, but the effect of the disease on blood vessels may be a factor, and some researchers have proposed that insulin and blood sugar regulation and variability could also play a role.

People can likely compensate for the degree of mental decline identified in the current study, Dixon said, by managing their diabetes, using their brain, and staying physically active.

SOURCE: Neuropsychology, January 2009.