INTRODUCTION:Subjective sleep quality may decrease during menstruation, although the duration and composition of sleep remains relatively stable across the menstrual cycle (MC) (1). Recording heart rate variability (HRV) is a tool to monitor the autonomic nervous system and recovery of the body. Meta-analytical data has not revealed significant changes in HRV from the early follicular phase (menses) to the mid-follicular phase (2). However, reduced HRV-values were observed during menses compared to follicular phase in women with pain during menses (dysmenorrhea) (3). Only a few studies have examined effects of the MC on nocturnal HRV. The aim of this study was to investigate how menses and associated pain affects nocturnal HRV and subjective sleep quality.METHODS:Participants included 14 healthy, physically active women, who did not use hormonal contraception. During one MC, participants completed a diary of sleep, MC and related symptoms. HRV was registered every night (Bodyguard 2, Firstbeat Technologies Ltd., Finland). HRV-data (RMSSD and LF/HF-ratio) were analyzed for two nights after a blood sample and over a four-hour period beginning 30 min after bedtime. Only the menses (M) and mid-follicular phases (FP) are used in this study. Blood samples (estradiol, E2, and progesterone, P4) were collected during M (day 2-3 of the MC) and FP (day 7-10) to ensure normal hormonal function associated with the MC (4).RESULTS:E2 was higher (p=0.012) during FP (267±150 pmol/L) compared to M (143±88 pmol/L), but P4 remained stable (p=0.103). Mean heart rate (HRmean) was higher during M (54±8 beats/min) compared to FP (52±7 beats/min, p=0.022). However, HRV-variables did not differ between M and FP (RMSSD: 76.7±34.5 to 77.3±27.0 ms, p=0.872; LF/HF: 1.416±1.380 to 1.273±0.769, p=0.826). Subjectively-assessed sleep quality remained unchanged between M and FP (p=0.349). The change in RMSSD and HRmean between M and FP did not differ (RMSSD: p=0.728; HRmean: p=0.149) between participants with and without menstrual pains.CONCLUSION:Menses has no effect on nocturnal HRV and subjective sleep quality of physically active women, though the higher nocturnal HRmean during M may indicate decreased recovery during menses.
REFERENCES:1. Driver, H.S., Werth, E., et al. The Menstrual Cycle Effects on Sleep. Sleep Med Clin 2008, 3:1–11.2. Schmalenberger, K.M., Eisenlohr-Moul, T.M., et al. A Systematic Review and Meta-Analysis of Within-Person Changes in Cardiac Vagal Activity across the Menstrual Cycle: Implications for Female Health and Future Studies. J Clin Med 2019, 8:1946.3. Jayamala, A.K., Preethi, B.L., et al. Comparative Analysis of Heart Rate Variability During Different Phases of Menstrual Cycle in Eumenorrhea & Dysmenorrhea Subjects. Exp Clin Physiol Biochem 2017, 1.4. Elliot-Sale, K.J., Minahan, C.L., et al. Methodological Considerations for Studies in Sport and Exercise Science with Women as Participants: A Working Guide for Standards of Practice for Research on Women. Sports Med 2021, 51:843–861.
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