Free-running sleep

Circadian rhythm

Sleep Stages

Non-rapid eye movement sleep

Neuroscience

Light effects on circadian rhythm

Dark therapy

Polysomnography

Endocrinology

Operating system

Computer science

Heart rate

Ultradian rhythm

Eye movement

Heart rate variability

Sleep (system call)

Blood pressure

Psychology

Circadian clock

Apnea

Internal medicine

Electroencephalography

Medicine

Morning

Wakefulness

Slow-wave sleep

SLEEP

Nocturnal cardiovascular events are more frequent at the beginning and end of the night. It was proposed that this pattern reflects the nocturnal distribution of sleep and sleep stages. Using heart rate variability (HRV), we recently showed an interaction between the circadian system and vigilance states on the regulation of cardiac rhythmicity. Here, we further investigate this interaction in order to clarify the specific effects of sleep stages on the regulation of the heart.Participants underwent a 72-h ultradian sleep-wake cycle procedure in time isolation consisting of alternating 60-min wake episodes in dim light and 60-min nap opportunities in total darkness.Time isolation suite.Fifteen healthy young participants; two were subsequently excluded.N/A.The current study revealed that sleep onset and progression to deeper sleep stages was associated with a shift toward greater parasympathetic modulation, whereas rapid eye movement (REM) sleep was associated with a shift toward greater sympathetic modulation. We found a circadian rhythm of heart rate (HR) and high-frequency power during wakefulness and all non-REM sleep stages. A significant circadian rhythm of HR and sympathovagal balance of the heart was also observed during REM sleep. During slow wave sleep, maximal parasympathetic modulation was observed at ∼02:00, whereas during REM sleep, maximal sympathetic modulation occurred in the early morning.The circadian and sleep stage-specific effects on heart rate variability are clinically relevant and contribute to the understanding of the degree of cardiovascular vulnerability during sleep.

Circadian Variation of Heart Rate Variability Across Sleep Stages