Acute hypoglycemia in humans causes attentional dysfunction while nonverbal intelligence is preserved

OBJECTIVE - Experimentally induced hypoglycemia in humans causes progressive but reversible cognitive dysfunction, but it is not known to what extent neuropsychological tests index abilities of cognitive functioning that are important in everyday life. This study examines the effects of acute insulin-induced hypoglycemia on attention and intelligence in nondiabetic humans.

RESEARCH DESIGN AND METHODS - A hyperinsulinemic glucose clamp was used to achieve controlled euglycemia (4.50 [0.22] mmol/l) and hypoglycemia (blood glucose 2.59 [0.19] mmol/1) in 20 healthy volunteers. Subjects were Studied on two occasions in a counterbalanced order. During each study condition, subjects completed parallel tests of cognitive function. Cognitive function was assessed by the Test of Everyday Attention and Raven's Progressive Matrices.

RESULTS - Hypoglycemia induced a significant deterioration in tests Sensitive to both visual and auditory selective attention. During hypoglycemia, attentional. flexibility deteriorated and speed of information processing was delayed. Sustained attention was preserved and intelligence scores did not deteriorate during hypoglycemia.

CONCLUSIONS - During hypoglycemia, a significant deterioration occurs in attentional abilities, whereas fluid intelligence is preserved. On the basis of these results, it can be surmised that many complex attention tasks relevant to everyday life are impaired during moderate hypoglycemia.