Many diabetics experience worse cognitive-motor functioning during periods of hyperglycemia that occur in the course of their daily routines, investigators report in the January issue of Diabetes Care.

Patients often report not feeling well when their blood glucose levels are high, lead author Dr. Daniel J. Cox told AMN Health, but lacking “a clear theory as to why that happens, patient complains were typically being ignored, because they did not fit into our theoretical models,” he said.

While laboratory studies have shown cognitive decrements when blood glucose is artificially raised in a controlled environment, “this is not a realistic environment,” the researcher added.

Dr. Cox of the University of Virginia Health System in Charlottesville and colleagues therefore conducted a field study in which they instructed subjects with type 1 and type 2 diabetes 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. Included were 196 subjects with type 1 diabetes and 34 with type 2.

Approximately 55% of subjects displayed increased errors and slower responses when blood glucose exceeded a threshold of around 15 mmol/L.

Two predictor variables - percentage of blood glucose levels > 15 mmol/L and performance during euglycemia - were associated with greater effects of hyperglycemia on cognitive function.

Dr. Cox pointed out that to avoid decrements in function associated with hypoglycemia, patients 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 extreme blood glucose levels.