High blood sugar, as well as low, slows the mind

Many people with diabetes find that they become mentally and physically sluggish during periods when their blood sugar level rises in the course of their daily routines, investigators report.

Most people with diabetes are aware of problems when their blood sugar levels drop too far. However, patients also often report not feeling well when their blood glucose levels are high, Dr. Daniel J. Cox told Reuters Health - but lacking "a clear theory as to why that happens, patient complaints were typically being ignored," he said.

While laboratory studies have shown that mental performance declines when blood glucose is artificially raised, "this is not a realistic environment," the researcher added.

Cox, at the University of Virginia Health System in Charlottesville, and his colleagues therefore conducted a field study with 196 subjects with type 1 diabetes and 34 with type 2 diabetes.

The team instructed the participants to complete tests assessing verbal and mathematical skills using hand-held computers immediately before routine self-monitoring of blood glucose, three to four times daily.

Approximately half the subjects made more errors and had slower responses when blood glucose exceeded a certain point, the researchers report in the medical journal Diabetes Care.

Cox pointed out that to avoid a drop in performance associated with low blood glucose, people often load up on carbohydrates before "cognitively sensitive procedures," such as exams.

"But they in fact could being doing themselves a significant disservice," he said, and would perform better by avoiding both high and low extremes of blood glucose levels.

SOURCE: Diabetes Care, January 2005.