OBJECTIVE: Acute hypoglycemia in humans impairs cognitive functions and alters mood states. The time required for cognitive functions and moods to return to normal after an acute episode of severe hypoglycemia is unknown. RESEARCH DESIGN AND METHODS: Cognitive functions and moods were studied prospectively in 20 subjects with insulin-treated diabetes who had recently experienced a spontaneous episode of severe hypoglycemia ("hypo" subjects) and 20 matched control subjects with insulin-treated diabetes who had not experienced severe hypoglycemia during the preceding year. The hypo subjects had a history of a greater number of episodes of severe hypoglycemia (P = 0.000). Cognitive function tests and mood scales were administered at 1.5, 9, and 30 days after the severe hypoglycemia and at similar intervals for the control subjects. RESULTS: For most of the cognitive tests, no evidence of a "hangover" effect of the acute hypoglycemia on cognitive function was observed (P > 0.05). A trend was noted for levels of hedonic tone (P = 0.082) and energetic arousal (P = 0.053) to improve with time in the hypo subjects but not in the control subjects. However, the hypo subjects had chronically elevated levels of depression (P = 0.011) and anxiety (P = 0.049) and persistently performed more poorly in several cognitive tests, such as the Digit Symbol Test (P = 0.009) and the Stroop Task (P = 0.007). CONCLUSIONS: These results suggest that, in general, recovery from any acute cognitive decrement after severe hypoglycemia was complete by 1.5 days. The cognitive decrements and altered mood states noted in the hypo subjects may be persistent and may be a consequence of previous exposure to recurrent episodes of severe hypoglycemia.

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