Well-Being, Cerebral Function, and Physical Fatigue After Nocturnal Hypoglycemia in IDDM

OBJECTIVE This study assessed the effect of nocturnal hypoglycemia on well-being cerebral function, and physical fatigue the next day in 10 subjects with IDDM.

RESEARCH DESIGN AND METHODS After an exercise test to determine work-loads corresponding to 30 and 60% VO_2max, volunteers were studied twice, 4 weeks apart. Blood glucose was lowered one night to 2.3–2.7 mmol/l for 1 h, and at the control visit, hypoglycemia was avoided. The next morning, well-being was assessed using the minor symptom evaluation profile (MSEP), and cerebral function was assessed with the paced auditory serial addition test, the digit symbol substitution test, trail making part B, four-choice reaction time, and auditory P300 latency. Subjects then exercised at predetermined workloads corresponding to 30% VO_2max for 30 min and 60% VO_2max until exhaustion. Fatigue was assessed every 10 min using the Borg scale for rating of perceived exertion.

RESULTS All three components of the MSEP scored higher (indicating more symptoms) after the hypoglycemic night compared with the control night (P < 0.01 contentment, sleep; P < 0.001 vitality). None of the cerebral function tests performed the next day was affected by hypoglycemia. Exercise capacity was similar at both visits, but subjects were more fatigued after the hypoglycemic night (P < 0.01, analysis of variance). There were no differences in potassium, catecholamine, glucose, or lactate concentrations between visits either before or during exercise.

CONCLUSIONS One hour of hypoglycemia at night affects a subject's sense of well-being, but not cerebral function, the next day. The greater fatigue after the hypoglycemic night cannot be explained by the biochemical parameters measured.