Research Article

Cognitive function during hypoglycaemia in type I diabetes mellitus.

Br Med J (Clin Res Ed) 1986; 292 doi: (Published 08 March 1986) Cite this as: Br Med J (Clin Res Ed) 1986;292:647
  1. S Pramming,
  2. B Thorsteinsson,
  3. A Theilgaard,
  4. E M Pinner,
  5. C Binder


    Neuropsychological testing was carried out in 16 insulin dependent (type I) diabetic men during four periods when mean blood glucose concentrations were (A) 6.3 (SEM 0.13) mmol/l (113.5 (SEM 2.3) mg/100 ml), (B) 2.9 (0.05) mmol/l (52.3 (0.9) mg/100 ml), and (C) 1.8 (0.03) mmol/l (32.4 (0.05) mg/100 ml), all measured during intravenous insulin infusion, and (D) 6.1 (0.13) mmol/l (109.9 (2.3) mg/100 ml), measured after intravenous glucose. The total neuropsychological test score decreased between periods A and B, A and C, and B and C, whereas improvement occurred between periods C and D (all p less than 0.02). These results were not due to changes in individual subjects alone but were consistent for the whole group. During hypoglycaemia there were changes in the patients' estimates of elapsed time, which were underestimated at period C as compared with the estimates at periods A, B, and D (all p less than 0.05). None of the 16 patients noticed symptoms of hypoglycaemia at period A or B, 12 reported symptoms at C, and one at D. Patients with type I diabetes may show a deterioration in neuropsychological skills during periods of asymptomatic subnormal or hypoglycaemic blood glucose concentrations.