THE FEMALE SLEEP PARADOX: WHY MANY FEMALE PLAYERS HAVE SLEEP AS A FOE WHEN IT SHOULD BE A FRIEND

Introduction

Sleep issues are significantly more common amongst athletes than the general population, partly due to the bodily and mental stress associated with performing at a high level, and the environmental demands of having to consistently travel and perform during evening matches1 However, there are also experiences specific to women that can compound these factors that influence sleep quality.

From the pain associated with menstrual cramps to the impact of hormones on melatonin production, female players will have additional risk factors to contend with in New Zealand & Australia this summer.

The Female Sleep Paradox

Several studies have found that women generally have better quality sleep patterns for athletic recovery. They spend more time in deep restorative sleep2, allowing them to recover quicker physically and create memories more readily. However, despite them spending more time in deep sleep, women paradoxically also more frequently report poor subjective sleep quality3 and are 55% more likely to report sleep disturbances than their male athlete counterparts4

Subsequently, the prevalence of insomnia is particularly high in women5, partly attributable to menstrual cramps (dysmenorrhea), endometriosis, hormonal fluctuations, and pregnancy. Despite sleep being considered as a potential performance advantage for female athletes, it can very quickly become a weakness without specialist individualised education and intervention.

Endometriosis

Endometriosis is a condition which results in the presence of endometrial glands and stroma like lesions outside of the uterus, and is a condition that affects women of any age. In 2022, England captain Leah

Williamson spoke out about the impact endometriosis has had on her life, and how following her diagnosis in 2021 she worried that the condition could have led to her missing key matches during England’s European Championship victory on home soil. These worries came from the ‘agonising’ pain she endured.

Endometriosis is characterised by particularly debilitating period pains, pelvic pains, cramps and uncomfortable bowel movements. Endometriosis is relatively prevalent affecting approximately 10% of women of reproductive age6

When it comes to sleep, research consistently shows that women with a diagnosis of endometriosis can expect:

• More sleep disturbances7

• Longer sleep onset latency7

• Worse subjective sleep quality8, with one study finding a 30% difference between those with and without endometriosis9

• And, subsequently, greater daytime sleepiness10

Crucially, it is those with the greatest pain intensity that have the biggest sleep problems10. This is as expected, with the pain of endometriosis making it difficult to relax enough to create sleep onset while also causing women to consistently wake up throughout the night. This is a finding that is showcased across the board with people who experience chronic pain11

The challenge for female footballers is that sleep and endometriosis can form a vicious cycle. Research has found that poor sleep quality one night generally leads to greater pain sensitivity the following day, making endometriosis symptoms even more debilitating12. These worsened endometriosis symptoms then lead to even worse sleep that night, and the vicious cycle continues. The result is fatigue being twice as common in individuals with endometriosis than in their control group counterparts13. Fatigue in turn impacts player performance as poor decision making occurs and sub-optimal physical intensity ensues. Further more fatigue secondary to poor sleep quality impacts recovery through overreach injuries and muscle fatigue accumulation.

On top of pain broadly impacting on sleep quality, endometriosis has also been associated with a sleep medical condition called Restless Leg Syndrome. This sleep condition is already more common amongst elite athletes, but research also suggests that those with endometriosis are 2 and a half times more likely to experience Restless Leg Syndrome (RLS) than the general population14 This could be due to the strong relationship between RLS and iron deficiency15, and women with endometriosis being at greater risk of iron deficiency through heavier menses and the iron unavailability associated with endometriosis-related chronic inflammation.

For women playing in this year’s world cup that are struggling with endometriosis symptoms, there are a few things to keep in mind that could help with their pain and/or RLS symptoms and their impact on sleep:

• Physical exercise is a protective factor against endometriosis. As Leah Williamson highlighted, her endometriosis flared up after getting a hamstring injury. Research suggests that regular physical exercise improves levels of immune and anti-inflammatory markers and reduces menstrual flow, which can then decrease the symptom weight for athletes16. Regular exercise can also enhance melatonin secretion, which subsequently helps endometriosis sufferers with insomnia symptoms17

• On top of exercising, which is of course a natural part of elite athletes’ lives anyway, melatonin supplementation might be a way to kill two birds with one stone. Clinical trials have found that treatment of 10mg of melatonin for 8 weeks, when compared with placebo in women with endometriosis, reduces daily pain, stomach cramps, painful urination, and improves sleep quality18. It is important to note that this study was not within the athletic population, though.

• As well as supplementing melatonin, as iron deficiency is strongly associated with endometriosis, and subsequently with RLS, female athletes at the World Cup should also consider discussing with their doctor about the need for iron supplementation.

• And finally, Leah Williamson described how the threat of a painful period provided additional stress and anxiety. Painful menses triggers additional stress and anxiety which in turn may result in insomnia, meaning that an individual who has a diagnosis of endometriosis might not only have poor sleep when they are in pain. Ruminating on the potential pain could be enough to worsen sleep onset, and potentially induce endometriosis symptom flare ups. Working with a clinically trained psychologist, especially those who specialise in sleep, can help tackle these psychological triggers for poor sleep.

Pregnancy

Another factor that influences the sleeping experiences of female athletes is pregnancy. Remarkably, a FIFPro report from 2017 which surveyed 3,295 women footballers found that only 2% were mothers19. Although this report didn’t survey any male players, we can expect this percentage to be significantly higher in the male population, in part because they don’t have to take time out of their career to carry a child. This is a particular issue because less than 40% of female players are offered childcare support and this means almost half of women footballers believe they would have to leave the game early if they wanted to start a family. This is supported by the view of leading coaches, with Emma Hayes describing the lack of childcare support offered to female players as a disgrace.

Therefore, due to the scarcity of women’s footballers who are mothers, we will spend less time talking about the impact that pregnancy has on sleep. That said, it’s important to highlight that there are multiple partum-related factors that impact on sleep:

• Sleep issues during pregnancy are highly common with almost half (46%) of women reporting poor sleep, and sleep issues become more common as women move from the second to the third trimester20.However, it is to be noted that even in the second trimester, over 1/4 of women (285) slept less than 7 hours per night21 and in the first trimester more than half of women report insomnia symptoms despite normal sleep duration22

• Although total sleep time increases during the first trimester, subjective sleep quality is altered as early as the first trimester

• Sleep then worsens throughout pregnancy with the end of pregnancy being associated with greater sleep fragmentation because of a number of variables21: snoring, respiratory effort-related arousals, restless leg syndrome, and lower back pain.

• Restless leg syndrome is potentially the most common sleep disorder associated with pregnancy, with systematic analyses suggesting a prevalence of between 26 and 30% for gestational restless leg syndrome23 With athletes already being at risk of restless leg syndrome, and women being twice as likely to experience restless leg symptoms compared to men, this is a key area that needs tackling. Residual postpartum RLS correlated with lower ferritin23, which again highlights the importance of supplementing iron as a way of tackling RLS’ impact on women’s sleep experiences.

Hormones, Cramps and the Menstrual Cycle

The primary sleep-regulating areas in the brain are filled with estrogen and progesterone receptors24, which is why it’s unsurprising that hormonal fluctuations in women have a significant impact on sleep quality. This is something that takes effect as young as after a woman’s first menstrual bleeding with research demonstrating that girls are 2.75 times more likely to develop insomnia when compared to boys25

The biggest hormone-driven sleep changes seem to be during the pre-menstrual fluctuation of progestogens and estrogens rather than during the follicular or luteal phases, with one study finding no difference in objective sleep data throughout these phases other than a higher percentage of restorative REM sleep in the follicular phase compared to the luteal phase26. However, due to non-hormonal factors associated with stages of the menstrual cycle that include bleeding, research shows a worsening of subjective indicators of sleep quality and efficiency, and total sleep time during the menstrual phases too27

Research shows that the sleep issues associated with the menstrual cycle are likely present in elite female athletes, too. During the menstrual phase, female athletes can expect to experience a decrease in the proportion of sleep time spent in restorative slow wave sleep27. The primary drivers of poor sleep quality during hormonal fluctuations is likely the increase in core body temperature seen when progesterone levels are elevated28

Pain during the menstrual cycle is an extremely common experience for women. Research by Women’s Health Concern suggests that over 80% of women will experience period pain at some point in their life. What this means is there is likely a time when women are more vulnerable to poor sleep quality through worse sleep onset

(struggling to relax and get to sleep), more sleep awakenings during the night, and a greater likelihood of waking up earlier than they want.

The tournament in New Zealand and Australia lasts a month. We can expect a significant proportion of players to experience menstrual cycle-related sleep issues during this tournament, purely based on their natural body clocks. What this means is that players and medical teams need to be prepared for the impact this could have by:

• Educating players on how they can prevent the menstrual cycle from significantly impacting their sleep, including sleeping in the foetal position for cramps, wearing loose fitting clothes and making sure their bedroom is cool so they don’t get too hot, and potentially increasing total sleep time for the few days before and during the menses phase

• Have sleep experts screen squads to identify players who are vulnerable to the impact of the menses phase on their sleep, and develop tailored strategies to help players effectively wind down before bed and optimise sleep/recovery during these more challenging periods

• It’s important for players to know how they can best be kind to themselves when struggling with their menses and that they can expect slightly worse during the menses phase. If players feel ready and equipped to tackle hormone changes, pain and slightly worse sleep when it comes by, they’re less likely to allow stress and anxiety to be another factor impacting their sleep.

What we should be doing

Part of medical and performance teams’ work with female athletes is helping them understand that there are unique factors associated with being a woman that could impact on their sleep, and they need to be fully prepared for this.

The first step in empowering female athletes to deal with the potential sleep challenges is to educate. Athletes and staff need to better understand the womanspecific factors that can negatively impact on the sleep quality of players, and part of this is creating a team culture where female athletes feel safe to talk about these issues. Previous research has shown that female athletes vary in how comfortable they are talking to male coaches about these issues29, and this is where representation becomes huge. If female athletes are not supported by staff which allow them to feel comfortable to discuss these issues whilst also being aware of the challenges these athletes face, then this population of athletes will continue to suffer in silence.

The second step is to measure the origin of symptoms. Without effective measuring of sleep, and the factors influencing sleep, it is impossible to provide tailored and targeted interventions for female athletes. For one athlete they might be struggling to sleep during their menstrual cycle because of cramps, for another it could be elevated progesterone levels leading to heightened body temperature. Without effective sleep screening and 1:1 consultation with players, both players could be given the same treatment for sleep disruption and perhaps only one would benefit. Crucially, there’s an overreliance in sports on wearable technology for sleep. Technology showing a player’s sleep stages without qualitative understanding and expert understanding offers little-tono value when trying to improve a player’s sleep quality. The sleep stage data might provide information on poor sleep patterns, but it would not provide information on psychological symptoms, restless leg syndrome or changes in breathing patterns. For this reason, medical and performance staff need to properly screen for sleep issues. This will help facilitate tailored interventions and guidance for each player.

Finally, female athletes should be encouraged to lean into their sport. Poor sleep quality and the pain associated with endometriosis, the menstrual cycle, and pregnancy can all make football feel like a chore. However, research suggests that women who regularly exercise have a significantly better sleep quality, so players should be reminded that their sport is actually a protective factor against poor sleep quality30

Okay, but why does good sleep quality even matter for female athletes?

As well as the significant performance, recovery and wellbeing gains seen in footballers who have better sleep quality, research suggests that extending sleep can help reduce inflammation, which has a significant impact on the likelihood of developing the negative symptoms associated with menstruation such as menstrual cramps31

Conclusion

There’s a female sleep paradox. Female athletes can make sleep-related recovery a strength but currently for many it is a weakness. Several players are struggling with their sleep in silence during pregnancy as they’re not being properly supported by the footballing world. There’s a growing awareness that endometriosis is a relatively common experience for female athletes, but there isn’t currently a discussion surrounding its vicious cycle with sleep and how this subsequently impacts performance and recovery.

The numerous factors impacting sleep quality can be conceptualised as multiple ‘vicious cycles’. Our ‘vicious flower’ diagram illustrates this (see figure 1 below). More practically, this can also be used to help the athlete make sense of their sleep problems, and key maintaining factors (‘petals’) can be targeted, thereby breaking these negative cycles.

Finally, in a tournament that lasts as long as the average woman’s menstrual cycle, medical and performance teams need to be considering the impact of the menstrual cycle on all their players’ sleep quality. The reality is that many athletes do not recognise they have sub-optimal sleep or they have become resigned to it. This suboptimal sleep is impacting female players’ performance, recovery and mental health/ wellbeing. Furthermore, the only genuinely viable way to tackle this is through specialist sleep screening and assessment of players, together with individually tailored sleep support delivered by clinically trained sleep experts.

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