Study objectives: In insulin-treated patients with diabetes, episodes of severe hypoglycemia often occur during sleep, which might reflect an altered counterregulation and reduced awareness. This study examined the influence of sleep on the counterregulatory response to hypoglycemia in healthy subjects.
Design: Subjects participated in two experimental conditions; statistical tests relied on within subject comparisons.
Setting: University hospital sleep laboratory.
Participants: 15 healthy young men.
Interventions: Hypoglycemia (2.8 mmol/l) was induced for 45 min by insulin infusion once during sleep and once at the same time of night while being awake.
Measurements and results: Counterregulatory hormone concentrations (epinephrine, norepinephrine, ACTH and cortisol) and sleep recordings were obtained. Differences in the hormonal responses to hypoglycemia between sleep and wake conditions remained non-significant, indicating that sleep does not exert a primary influence on the strength of counterregulation. However, the glycemic threshold for the onset of counterregulation was significantly changed during sleep: The average onset threshold for epinephrine and norepinephrine counterregulation was 3.3 +/- 0.1 mmol/l for the wake condition and 2.7 +/- 0.1 mmol/l for the sleep condition (P < 0.001). A decrease in sleep depth coincided with the onset of the counterregulatory response, with most subjects showing signs of awakening.
Conclusions: During sleep, the organism is less sensitive to hypoglycemia. Hypoglycemia per se has an awakening effect.