Psychomotor Performance and Counterregulatory Responses During Mild Hypoglycemia in Healthy Volunteers

Abstract

The effect of mild hypoglycemia on psychomotor performance and counterregulatory responses was studied among 12 healthy volunteers. Each volunteer received two modified hyperinsulinemic glucose clamps. One morning, plasma glucose was held constant at euglycemic levels (4.9 mM) for 95 min, and another morning, it was lowered over 35 min and then held constant at hypoglycemic levels (3.4 mM) for 60 min. A battery of psychomotor tests and a questionnaire assessing hypoglycemic symptoms were administered before and repeated during the last 30 min of each clamp. The questionnaire and three selected psychomotor tests were also administered repetitively during the 1st h of each clamp. During the hypoglycemic studies, a rise was seen in plasma epinephrine and pancreatic polypeptide at 45 min. An increase in symptom scores was first recorded at 50 min during the hypoglycemic studies [median 4 (range 0-13) vs. 2 (5-6), P less than .05]. Performance was impaired on two psychomotor tests included in the battery. One was the trail making test on fine motor performance (-19.3 +/- 4.2 targets/min, mean +/- SE vs. 1.2 +/- 4.8 targets/min, P less than .05), and the other was the digit-symbol substitution (DSS) test on information processing and memory (18 +/- 3 vs. 29 +/- 4 symbols/min, P less than .03). Of the tests administered during the 1st h, performance was impaired on the DSS. This impairment became significant at 45 min (14 +/- 4 vs. 22 +/- 4 symbols/min, P less than .005). In conclusion, mild hypoglycemia selectively impairs psychomotor performance in healthy volunteers but not before the onset of glucose counterregulation and warning symptoms.

Short-Term, Delayed, and Working Memory Are Impaired During Hypoglycemia in Individuals With Type 1 Diabetes

“…In addition, performance in the Trail Making B Test and the Digit Symbol Test was impaired significantly during hypoglycemia. This is consistent with previous observations (9,11,12,17,22) and confirms that the degree of hypoglycemia achieved was sufficient to affect other domains of cognitive function.…”

“…In addition to the memory tests, the Trail Making B Test and the Digit Symbol Test were also administered. These tests were used to confirm the effect of hypoglycemia on cognitive function, as has been shown in previous studies (9,11,12,17,22).…”

Beta‐adrenoceptor blockade and hypoglycaemia. A randomised, double‐ blind, placebo controlled comparison of metoprolol CR, atenolol and propranolol LA in normal subjects.

“…Our findings are reassuring in this respect and in agreement with others (Ogle et al, 1976;Van Rooy et al, 1985); 3-adrenoceptor blockers did not prolong reaction time during euglycaemia, and at a blood glucose of 2.5 mmol 1-1 had no additive effect over and above that of hypoglycaemia. However, four-choice reaction time is a psychomotor test and it is possible that tests measuring different aspects of cognition (Stevens et al, 1989) might have shown an adverse effect of 3-adrenoceptor blockers.…”

Acute Hypoglycemia in Humans Causes Attentional Dysfunction While Nonverbal Intelligence Is Preserved

“…General intelligence is a key finding and theoretical construct in the psychometric structure of human abilities (16) and is an important influence on many everyday activities (17). Although some studies of acute hypoglycemia have shown a deterioration in aspects of intelligence in both patients with diabetes (7,18) and nondiabetic subjects (19,20), previous studies in humans have not included subtests that were designed specifically to measure aspects of nonverbal intelligence.…”