Robust circadian rhythm in heart rate and its variability: influence of exogenous melatonin and photoperiod

Abstract

SUMMARY Heart rate (HR) and heart rate variability (HRV) undergo marked fluctuations over the 24-h day. Although controversial, this 24-h rhythm is thought to be driven by the sleepwake/rest-activity cycle as well as by endogenous circadian rhythmicity. We quantified the endogenous circadian rhythm of HR and HRV and investigated whether this rhythm can be shifted by repeated melatonin administration while exposed to an altered photoperiod. Eight healthy males (age 24.4 ± 4.4 years) participated in a double-blind cross-over design study. In both conditions, volunteers were scheduled to 16 h-8 h rest : wake and dark : light cycles for nine consecutive days preceded and followed by 29-h constant routines (CR) for assessment of endogenous circadian rhythmicity. Melatonin (1.5 mg) or placebo was administered at the beginning of the extended sleep opportunities. For all polysomnographically verified wakefulness periods of the CR, we calculated the high-(HF) and low-(LF) frequency bands of the power spectrum of the R-R interval, the standard deviation of the normal-to-normal (NN) intervals (SDNN) and the square root of the mean-squared difference of successive NN intervals (rMSSD). HR and HRV variables revealed robust endogenous circadian rhythms with fitted maxima, respectively, in the afternoon (16:36 hours) and in the early morning (between 05:00 and 06:59 hours). Melatonin treatment phase-advanced HR, HF, SDNN and rMSSD, and these shifts were significantly greater than after placebo treatment. We conclude that endogenous circadian rhythmicity influences autonomic control of HR and that the timing of these endogenous rhythms can be altered by extended sleep/rest episodes and associated changes in photoperiod as well as by melatonin treatment.k e y w o r d s circadian, constant routine, heart rate, heart rate variability, light, melatonin, sleep

Heart rate variability and endothelial function after sleep deprivation and recovery sleep among male shift and non-shift workers

“…In addition to differences between the groups, the HRV data also showed significant effects of time of day. Changes within a day and circadian rhythms with peaks in the early morning have been previously reported in LF, HF (57), and SDNN (57-59), but not in other HRV parameters such as LF/HF (57, 58). This study aimed not only to compare shift and nonshift workers but also to investigate the effects of sleep deprivation and recovery sleep on FMD and HRV.…”

PER3 polymorphism and cardiac autonomic control: effects of sleep debt and circadian phase

“…The CR protocol has previously been used to asses the circadian regulation of autonomic control of the heart (26,53). It serves to verify endogenous circadian rhythms by either removing masking effects or distributing masking effects uniformly over the study period (18).…”

“…Sympathetic activity is higher during wakefulness than sleep, and, within sleep, the sympathetic contribution is greater in rapid eye movement (REM) sleep than in deep non-REM (NREM) sleep (7, 56). During continuous wakefulness under controlled behavioural conditions, HRV is not constant but varies with circadian phase such that global HRV is greatest in the early morning hours (25,30,32,44,52,53). The impact of sleep, wakefulness, and circadian phase on autonomic control of HRV is also of interest because the frequency of onset of acute myocardial infarctions shows a marked circadian variation.…”

Human Circadian Phase Estimation from Signals Collected in Ambulatory Conditions Using an Autoregressive Model

“…The circadian dynamics of HRV have been assessed in various studies such as those by Scheer et al (1999), van Eekelen et al (2004, Vandewalle et al (2007), and recently Boudreau et al (2012). However, its relevance to phase estimation has been underestimated.…”

“…Although the circadian rhythmicity of the HRV signal has been confirmed in a number of studies (Scheer et al, 1999;van Eekelen et al, 2004;Vandewalle et al, 2007;Boudreau et al, 2012), the signal is not used as a circadian marker or as a circadian phase predictor due to its high proneness to masking effects. Both heart rate and HRV can be subject to masking effects from body posture, meals, physical and mental activity, sleep/wake cycle, or stress (Hayano et al, 1990).…”