Verbal fluency and naming performance in type I diabetes at different blood glucose concentrations

The effect of serum glucose alterations on selected verbal skills was examined in a group of diabetic men between 18 and 35 yr of age. An artificial insulin infusion system was used to set and maintain glucose concentrations during testing at each of three levels: hypoglycemia (55 mg/dl), euglycemia (110 mg/dl), and hyperglycemia (300 mg/dl). Subjects were used as their own controls, with performance at euglycemia serving as the comparison standard. A double-blind crossover design was employed as described in Holmes et al. (see ref. 14). Results showed significantly disrupted naming or labeling skills at hypoglycemia, with a trend toward poorer performance at hyperglycemia. During hypoglycemia, rate of responding was slowed from 6% to 18%, compared with euglycemic performance, but accuracy was not impaired. In contrast, word recognition skills were not affected by deviations in glucose. These performance effects were not correlated with duration of disease except for one of the five tests administered. This one exception, on the most difficult task, was less notable than the general finding of no relation between disease duration (from 6 mo to 17.5 yr) and test performance. Thus, in addition to considering long-term consequences of blood glucose alterations, clinicians and diabetic patients may wish to consider acute neuropsychological consequences of disrupted euglycemia.