Diabetes Care, Vol 21, Issue 3 341-345, Copyright © 1998 by American Diabetes Association
Well-being, cerebral function, and physical fatigue after nocturnal hypoglycemia in IDDM
P King, MF Kong, H Parkin, IA Macdonald and RB Tattersall
Diabetes Unit, Queen's Medical Centre, Nottingham, U.K.
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% VO2max, 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%
VO2max for 30 min and 60% VO2max 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.