THE EFFECT OF IQ LEVEL ON THE DEGREE OF COGNITIVE DETERIORATION EXPERIENCED DURING ACUTE HYPOGLYCEMIA IN NORMAL HUMANS

Acute hypoglycemia provokes a deterioration in cognitive function both in normal individuals and patients with Type 1 diabetes. A large inte rindividual variation is observed in the magnitude of the cognitive dy sfunction observed during hypoglycemia, the reasons for which are not apparent. This study examines whether IQ level exerts a differential e ffect on the impairment of cognitive performance induced during acute hypoglycemia. Twenty-four nondiabetic participants were divided into h igh and average IQ groups according to their results on the Alice Heim 4 test and the National Adult Reading Test. Cognitive function was as sessed during hypoglycemia using the following cognitive test battery: Paced Auditory Serial Addition Test (PASAT), Rapid Visual Information Processing (RVIP), Trail-Making B (TMB), Digit Symbol Substitution Te st (DSST), and Four-Choice Reaction Time (CRT). In Condition A (the pl acebo condition), the participants' blood glucose was maintained at 4. 5 mmol/l throughout. On two occasions (Conditions B and C), the blood glucose was stabilized at 4.5 mmol/l for 30 min, lowered to 2.5 mmol/l (hypoglycemia) for 60 min, and restored to 4.5 mmol/l for 30 min. Und er each condition, the cognitive test battery was performed immediatel y after stabilization of blood glucose at 4.5 mmol/l, and the battery was repeated as follows: Condition A-after a further 40 min of euglyce mia; Condition B-after 5 min of hypoglycemia; Condition C-after 40 min of hypoglycemia. Multivariate analysis of variance demonstrated a det erioration in cognitive performance as a result of hypoglycemia irresp ective of IQ group (p < .005). Acute hypoglycemia induced a significan t deterioration in cognitive function in all tests except TMB (p < .05 ). No overall effect of IQ on deterioration in cognitive performance c ould be ascertained, although univariate analysis of variance revealed an IQ effect on two of the tests: The average IQ group deteriorated s ignificantly less than the higher IQ group during hypoglycemia in the 4-s PASAT task (p = .03) and tended to have higher false alarm rates i n the RVIP test (p = .06). In conclusion, individuals with a higher IQ do not appear to be protected from the adverse effects of acute hypog lycemia on cognitive function.