Sleep is arguably one of the most important tools for recovery amongst the athlete population due to its ability to influence a wide range of physiological functions.1 Despite this, sleep is evidently not prioritised, as reports show that athletes have a poorer quality of sleep compared to the general population, and often do not reach the recommended 8 hours per night.2,3 This can likely be attributed to the athlete lifestyle, which consists of intense training, travelling, and anxiety before important competitions, therefore making it very challenging for athletes to maintain good sleeping habits. But how does sleep quality differ between male and female athletes?
For further information about the importance of sleep, have a read of our previously published article, which outlines how to optimise sleep, and why it is so important to do so amongst athletes.
As with many topics within the field of sports science, it is not yet fully understood how and why characteristics of sleep vary between the sexes. As more data is emerging, it is becoming evermore apparent that there are sex differences in athlete sleep patterns, emphasising the need for females to be investigated as a separate population in order to determine optimal sleeping strategies for training. Patterns from recent data have found that while female athletes objectively sleep better than males (in terms of time and efficiency of sleep), they often report poorer quality of sleep and greater sleep disturbances.4,5 Although this paradox cannot yet be explained, it is thought that the menstrual cycle may play a role, as some studies have found evidence of sleep disturbances in the pre-menstrual phase.6 Indeed, female sex hormones (oestrogen and progesterone) have receptors in the area of the brain that regulates sleep, so it would make sense that fluctuations in these hormones throughout the cycle could have an impact.7
To understand why this is the case, Hrozanova et al.8 set out to investigate objective and subjective measurements of sleep in male and female athletes in a recently published paper. They also investigated measures of sleep across different phases of the menstrual cycle to determine whether fluctuating sex hormones could explain the differences seen between men and women. Here’s what they found…
The Study:
A total of 56 junior endurance athletes were recruited for the study, consisting of 37 men and 19 women. They were each provided with a sleep monitor to use throughout a 61-day period, that could effectively monitor time awake and asleep, as well as distinguish between the different sleep stages: light, deep, and rapid eye movement (REM). Other objective variables that were measured included time in bed, sleep latency (time to fall asleep), total sleeping time, and sleep efficiency. During this period, subjective measures were also recorded via daily sleep experience and well-being questionnaires. To understand whether differences in training load could account for the variations in sleep quality, all athletes recorded their training sessions by noting the time spent in each intensity domain.
As well as all of these measures, the female athletes underwent further investigation to understand more about the influence of the menstrual cycle. Across the 61 days, the athletes noted when they experienced menstrual bleeding, and from this, their menstrual calendar was deduced. The individual’s length of the cycle (e.g. 28 days) was divided by two to determine when ovulation occurs. The duration from menstrual bleeding to ovulation was labelled the follicular phase, and the duration from ovulation to menstrual bleeding was labelled the luteal phase. Overall, measures of sleep were recorded and compared between 4 phases: menstrual (bleeding days), pre-menstrual (the 3 days prior to bleeding), follicular and luteal phases. If you want to learn more about the phases of the menstrual cycle, we have briefly outlined them in a previous article.
Sex differences in sleep:
The first major finding of this study was that objective measures of sleep were better amongst the female athletes compared to the males. Prominent sex differences existed in many aspects of the sleep cycle. For example, female athletes had significantly greater time asleep, a longer time spent in light and REM sleep, less time until their first REM stage, and superior sleep efficiency. Further statistical analysis deduced that sex could explain 25% of the variance in the total time asleep, 28% of the variance in REM sleep, and 13% of the variance in sleep efficiency. It is important to note that well-being and training loads were very similar between the men and women, so we can rule them out as contributing factors. Despite this trend, women reported significantly poorer sleep quality in the daily questionnaire, once again demonstrating the existence of a sleep quality paradox.
Sleep & the menstrual cycle:
The second major finding of this study was the effect of menstrual cycle phase on markers of sleep quality. Compared to the remainder of the cycle, women spent more time in bed, greater time in deep sleep, and less time in light sleep on bleeding days. In the pre-menstrual phase, women had less time in light and deep sleep, and a shorter interval before their first REM stage compared to the menstrual phase. Finally, sleep efficiency was lower in the follicular phase versus the luteal phase, concomitant to an increase in deep sleep.
All together, these findings suggest that fluctuations in oestrogen and progesterone across the menstrual cycle could impact sleep quality in female athletes and therefore affect their ability to recover from training. The authors propose that blood loss from menstruation places an additional load on the body that increases the need for downtime, which may explain the increased time in bed. One must also consider the role of mood changes and physical pain, as nearly a third of the participants reported that they can impact their sleep.
Summary
While studies have previously shown that females achieve objectively better, but subjectively worse sleep, Hrozanova et al.8 are the first to show that sex differences exist within the stages of the sleep cycle (light/deep/REM) in an athlete population. Menstruating female athletes were shown to experience fluctuations in their sleeping patterns throughout their cycle, suggesting that sex hormones could influence their recovery. While the impact of the menstrual cycle remains poorly understood, these findings highlight the need to consider the needs of male and female athletes separately, such that training and recovery strategies can be suitably optimised to each biological sex.
References
- Vitale KC, Owens R, Hopkins SR, Malhotra A. Sleep Hygiene for Optimizing Recovery in Athletes: Review and Recommendations. Int J Sports Med. 2019;40(8):535-543. doi:10.1055/a-0905-3103
- Leeder J, Glaister M, Pizzoferro K, Dawson J, Pedlar C. Sleep duration and quality in elite athletes measured using wristwatch actigraphy. J Sports Sci. 2012;30(6):541-545. doi:10.1080/02640414.2012.660188
- Lastella M, Roach GD, Halson SL, Sargent C. Sleep/wake behaviours of elite athletes from individual and team sports. Eur J Sport Sci. 2015;15(2):94-100. doi:10.1080/17461391.2014.932016
- Carter JR, Gervais BM, Adomeit JL, Greenlund IM. Subjective and objective sleep differ in male and female collegiate athletes. Sleep Health. 2020;6(5):623-628. doi:10.1016/j.sleh.2020.01.016
- Koikawa, N., Shimada, S., Suda, S. Sex differences in subjective sleep quality, sleepiness, and health-related quality of life among collegiate soccer players. Sleep Biol. Rhythms. 2016;14:377–386. doi:10.1007/s41105-016-0068-4
- Romans SE, Kreindler D, Einstein G, Laredo S, Petrovic MJ, Stanley J. Sleep quality and the menstrual cycle. Sleep Med. 2015;16(4):489-495. doi:10.1016/j.sleep.2014.12.001
- Shughrue PJ, Lane MV, Merchenthaler I. Comparative distribution of estrogen receptor-alpha and -beta mRNA in the rat central nervous system. J Comp Neurol. 1997;388(4):507-525. doi:10.1002/(sici)1096-9861(19971201)388:4<507::aid-cne1>3.0.co;2-6
- Hrozanova M, Klöckner CA, Sandbakk Ø, Pallesen S, Moen F. Sex differences in sleep and influence of the menstrual cycle on women’s sleep in junior endurance athletes. PLoS One. 2021;16(6):e0253376. Published 2021 Jun 17. doi:10.1371/journal.pone.0253376
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THE PACE 