Why the study?
How do cardiac activity measures change during the transition from wakefulness to sleep?
How do cardiac activity measures change during the transition from wakefulness to sleep?
Heart rate and respiration rate decrease during the transition to stable Stage 2 sleep, with transient heart rate increases following spontaneous arousals.
Should not yet alter sleep monitoring; leaves open links to CV risk in prospective cohorts.
Alterations in a number of measures of cardiac activity were examined during sleep onset in 6 participants over 3 experimental nights. Each sleep onset was divided into four consecutive phases: wakefulness, mixed alpha and theta activity, stage 2 NREM sleep with arousals, and stable stage 2 sleep. The variables measured were heart rate (HR), respiratory sinus arrhythmia (RSA), pre-ejection period (PEP) and T-wave amplitude (TWA). Respiration rate (RR) was also measured. HR and RR were lower in stable Stage 2 sleep compared with wakefulness, whereas PEP, TWA and RSA did not change significantly. During the second and third phases of sleep onset, HR decreased at each transition into sleep and increased following each spontaneous arousal. This increase resolved rapidly, with a return to sleep levels by 12 beats after the arousal. HR changes are discussed with reference to RSA, PEP, TWA and the concept of a waking reflex.
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Burgess et al. (1999) studied this question.
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