de Zambotti M., Baker F.C. (2021) Sleep and Circadian Regulation of the Autonomic Nervous System. In: Chokroverty S., Cortelli P. (eds) Autonomic Nervous System and Sleep. Springer, Cham.
Sleep and the autonomic nervous system (ANS) are intimately connected. The ANS is under the influence of circadian and sleep-dependent modulation. Forced desynchrony and constant routine protocols indicate strong circadian influences on heart rate (HR) and cardiac vagal activity, which fluctuate across 24 hours, with HR being lower, and vagal activity higher, during the nocturnal period. Sleep also influences ANS activity: during non-rapid-eye-movement (NREM) sleep, sympathetic activity is lower and vagal functioning is higher, compared to rapid-eye-movement (REM) sleep, where ANS activity is more similar to wakefulness. A change in ANS innervation of the heart and vasculature drives the wake-to-sleep reductions in blood pressure, HR, and systemic vascular resistance. The reduction in cardiovascular activity during sleep, prominent during NREM sleep, plays a key role in maintaining cardiovascular health, providing a “cardiovascular holiday.” Sleep-dependent as well as circadian regulation of vagal activity is evident very early in life and persists across adulthood. There is some evidence of sex differences in sleep-dependent vagal activity in adolescents as well as female hormone effects on nocturnal ANS measures, although further work is needed to determine the significance of these effects.