Heart rate variability in healthy humans during night sleep

Polysomnography has been performed and heart rate variability has been studied during night sleep in healthy young subjects of both sexes. It has been shown that, on average, a shift in autonomic support towards parasympathicotonia occurs during sleep, with a maximum at stages III and IV of NREM sleep. At stage II of NREM sleep and during REM sleep, a short-term activation of the sympathetic nervous system comparable to wakefulness is observed.