Timing Modulates the Effect of Sleep Loss on Glucose Homeostasis.

CONTEXT Chronobiological factors may modulate the impact of sleep loss on glucose homeostasis. However, these interactions have not been systematically assessed in humans. OBJECTIVE To assess the effect of sleep loss during the late vs early night on glucose homeostasis. DESIGN Fifteen normal-weight men participated in three conditions of a randomized, balanced crossover study comprising two conditions with shortened sleep (i.e., 4 hours of sleep during the first or the second half of the night) and a control condition with 8 hours of sleep. Glucose, insulin, cortisol, and glucagon were measured. Insulin sensitivity and secretion were assessed with a Botnia clamp. RESULTS Compared with regular sleep duration, sleep loss reduced insulin sensitivity (M-value; P = 0.031) irrespective of early- or late-night timing (P = 0.691). The disposition index (i.e., the β-cell response adjusted for insulin sensitivity) also tended to be impaired by short sleep (P = 0.056) but not by sleep timing (P = 0.543). In contrast, sleep loss in the second half but not the first half of the night induced reductions in morning glucagon and cortisol levels (P < 0.031) followed by a transient increase in cortisol (P < 0.044). CONCLUSIONS Although sleep deprivation acutely reduced insulin sensitivity irrespective of its nocturnal timing, sleep loss in the early morning compromised α-cell and hypothalamic-pituitary-adrenal axis activity to a greater extent than sleep loss in the first half of the night. This pattern suggests that the timing of sleep restriction can partly potentiate its deleterious metabolic effects.