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Sleep and fertility are natural components of human life, but both are easily disrupted. For the 6.1 million American women who struggle with infertility, it’s possible that sleep and sleep dysfunction may play a role in their ability to conceive.
New research is diving deeper into the complicated relationship between sleep and fertility for both men and women, offering insight into the delicate complexity of the reproductive cycle.
In this article, we’ll look at the science behind the fertility-sleep connection, discover how sleep disorders each have their own impact on infertility, and share our favorite advice on how to improve your sleep health.
To understand why sleep has the power to impact fertility, it’s critical to also understand how important sleep is to our physical and mental health.
Sleep consists of three distinct stages: light sleep, deep sleep, and REM sleep. All three are crucial for our well-being, and anything which impacts either the total amount of time spent asleep or the duration of stages can impact us in a wide range of ways.
This is because we sleep for many reasons, not just one. Scientists are still studying the various benefits of sleep, including:
Sleep is also closely tied to circadian rhythms, which function as an internal clock. Your circadian rhythm dictates when you feel tired, sleep, and wake, but it also governs all the other patterns of your body. As this includes the production and fluctuation of hormones, circadian rhythms are particularly important when considering fertility.
CDC initiatives suggest seven hours of sleep a night for adults over the age of 21, but a third of Americans fall short of this goal. Signs indicate that poor sleep becomes more prevalent as we age, as a study of Americans over the age of 50 found that only 32% reported getting enough sleep.
Aside from their impact on fertility, sleep deprivation and sleep dysfunction are associated with a long list of ailments. These include daytime exhaustion, mood disorders (such as anxiety and depression), weight gain, a higher risk of disease (including cardiovascular disease, type 2 diabetes, and cancer), memory problems, and higher levels of stress hormones and inflammation markers.
Given the importance of sleep and the impact poor sleep can have on your mind and body, it’s no surprise that sleep also plays a role in fertility.
Causes of Infertility. Generalized causes on the left and specific causes on the right.
The American Society for Reproductive Medicine defines infertility as “the failure to achieve a successful pregnancy after 12 months or more of appropriate, timed unprotected intercourse or therapeutic donor insemination.” In women over the age of 35, the time limit may drop to six months.
American women have an infertility rate of approximately 15.5%. This number climbs to 24.3% for women who have never previously given birth. Another study estimates that around 6.1 million American women have struggled with infertility to some degree.
There is no one cause of, or treatment for, infertility. As we’ve covered, fertility is the result of a complicated coordination of bodily processes and hormones in both men and women. Just as the causes of infertility vary widely between individuals, so do treatments.
However, if you struggle with sleep dysregulation or a sleep disorder, it is possible that poor sleep or circadian rhythm dysfunction is impacting your fertility.
Fertility, like sleep, is a complicated process. The finely-tuned mechanisms of the reproductive cycle are still being studied, as is sleep, so the places where they interact are still in the early stages of research and understanding. However, initial studies are clear on the link between sleep and fertility.
Sleep can have an effect on hormones, but the menstrual cycle itself can cause fluctuations to circadian rhythms in addition to having an impact on overall sleep quality. While menstruating women without pain report sleep disturbances, these complaints worsen in severity for women suffering from premenstrual syndrome or menstrual pain. Pregnancy can also cause similar sleep health problems.
In the other direction, poor sleep, sleep deprivation, and circadian rhythm disruptions can all impact hormone levels in ways which are not yet fully understood.
The majority of research on the subject has focused on the impact of circadian rhythm disruptions. Shift workers, for instance, have long been known to have prolonged menstrual cycles and more incidence of abnormally heavy flow and severe menstrual pain.
Melatonin, a hormone associated with the sleep-wake cycle, is thought to be a potential cause of these effects. Shift workers are known to have abnormal melatonin levels when compared to the general population. In addition to sleep, melatonin also influences the immune system, controls reproductive hormones, and may play a role in egg fertilization and embryo viability.
The above graph demonstrates how melatonin (the hormone most closely related to sleep) production changes throughout the menstrual cycle. This is indicative of the relationship between sleep and the menstruation, suggesting fertility plays a role in how well one sleeps.
Of course, melatonin is not the only hormone involved in sleep and fertility. Research on the interaction between estrogen and circadian rhythms has been limited but may also prove to be important. “Clock genes” are related to the expression of circadian rhythms as well as successful reproduction, and estrogen is known to modify the effect of these genes in the reproductive system. One sign that estrogen and circadian rhythms are further linked is that polycystic ovary syndrome (PCOS), a significant cause of infertility in women, is associated with both disordered sleep and abnormal estrogen levels.
Two other hormones which are being studied in the context of sleep and fertility are prolactin and follicle-stimulating hormone (FSH).
Like melatonin, prolactin is secreted from the pituitary gland. While its name references its role in prompting lactation, prolactin also affects fertility and fluctuations are associated with PCOS and lack of normal ovulation. As with many other hormones, prolactin is released at higher levels during sleep and production is suppressed by sleep dysfunction and poor sleep quality.
FSH, on the other hand, has a less obvious connection to sleep. However, levels of FSH were 20% lower in women who slept for less than seven hours a day when compared to women getting enough sleep, even when factors like age and weight were accounted for. Both abnormally high and low levels of FSH are known to have profound reproductive effects.
Finally, the mental impact of sleep can’t be discounted when considering the relationship between sleep and fertility. Sleep dysfunction is associated with an increased risk of mood disorders such as depression and anxiety. While the impact of mental health on the reproductive cycle is also an area in need of further study, some research has shown that anxiety and distress can lead to lower rates of pregnancy.
Although male fertility is not as complicated as female fertility, it is still complex enough to affect sleep and sleep problems.
Not sleeping enough and sleeping too much are both associated with male fertility problems. Men in these categories were 42% less likely to conceive with their partner, while men who reported having problems sleeping more than half the time were 28% less likely to conceive.
There may be several reasons for this effect. Low levels of testosterone, for example, are known to result in a lower sperm count. Like other hormones, testosterone can be influenced by a wide range of factors. Sleep deprivation and stress are both known to result in low testosterone levels.
This graph shows the testosterone levels of a control group vs. people who have been sleep deprived (slept less than recommended) for four days (SD4) and people who have been sleep deprived for seven days (SD7).
Another potential culprit is anti-sperm antibody (ASA) production. In one study of men who fell asleep past midnight, ASA levels were higher than in those who went to bed between 10 P.M. and midnight. This study also showed low sperm counts and lower rates of sperm survival in the late-sleeping group.
As in women, circadian rhythms also influence fertility in men. Studies with mice have shown that when “clock genes” were deleted or mutated, both circadian rhythms and reproductive abilities were disrupted in both male and female mice.
While further research is needed to understand the impact circadian rhythm disruptions have on humans, we do know that male fertility is linked to the sleep-wake cycle. Semen collected before 7:30 A.M. has a much higher sperm count and concentration when compared to semen collected later in the day, as well as having a higher proportion of healthy, normal sperm. Seasonal changes also have an impact, with sperm count increasing throughout spring and decreasing in summer.
Assisted reproductive technology (ART) is best understood as a range of treatments for infertility. However, the success of these treatments can also be influenced by sleep and sleep dysfunction.
In-vitro fertilization (IVF) is the most common form of ART, while other types include intrauterine insemination and third-party assisted ART. Women undergoing IVF keep close track of their hormone levels, and research suggests that two of those hormones — follicle stimulating hormone (FSH) and melatonin — are particularly important to IVF while also being influenced by sleep.
FSH is one of the hormones that controls the menstrual cycle. In the average woman, FSH levels peak just before ovulation. As previously discussed, women who sleep fewer than seven hours a night have FSH levels 20% lower than women who sleep for seven or more hours.
While both high and low levels of FSH can impact reproduction in different ways, candidates for IVF are primarily concerned with abnormally high levels. The research is still ongoing as to whether high FSH levels correlate with poor IVF outcomes, but many ART clinics do not accept clients with FSH levels above a certain cut-off. In this case, it seems possible that too much sleep may be more of a concern than too little sleep, but research on sleep and FSH is still in the early stages.
More research has been done on melatonin, although there is still much researchers do not know about its potential role in IVF.
In addition to influencing (and being influenced by) circadian rhythms and playing a role in the menstrual cycle, melatonin is also a powerful antioxidant. Oxygen damages cells and is particularly dangerous for embryos. In IVF the embryo is temporarily outside the womb and therefore exposed to more oxygen, so studies have begun to examine whether melatonin might offer protection against this damage.
Male fertility is rarely given as much attention in IVF research, but poor seminal quality can still affect IVF success rates. Melatonin may play a role here as well, as it has been shown to improve the quality of semen samples through neutralizing oxygen and nitrogen. Studies on both animals and humans have indicated that adding melatonin results in improvements to sperm count, mobility, and viability.
As with fertility in general, sleep dysfunction can also impact the success of ART treatments by affecting both physical and mental stress levels.
One study showed that 45-75% of women undergoing IVF regularly slept for less than seven hours a night, resulting in both elevated inflammation markers and increased anxiety. The impact of reduced sleep on IVF success is still unknown, but researchers involved in the study believe their results show that treating sleep loss may be useful in improving IVF outcomes.
This flowchart shows ways in which lack of sleep (sleep dysfunction) is associated with various issues known to cause infertility.
The International Classification of Sleep Disorders places sleep disorders into six major categories:
All sleep disorders can interfere with sleep and potentially fertility. However, the majority of research on the connection between infertility and sleep has focused on insomnias, sleep-related breathing disorders (particularly obstructive sleep apnea), and circadian rhythm sleep-wake disorders.
If you suffer from sleep dysfunction or believe you do, speak to your doctor. Not only will they be able to direct you towards the most effective treatment, but proper diagnosis will give you and your care team a better understanding of the effect it may have on your fertility.
Obstructive sleep apnea is a common sleep-related breathing disorder. People who suffer from OSA stop breathing multiple times every night when the tissue and muscles of their throat become overly relaxed and block airflow. (Snoring, a common symptom of OSA, is the result of tissue and muscle vibration.) When the airway becomes blocked, blood oxygen levels decrease, which results in an increased heart rate and the possibility of waking up with a gasp to regain normal breathing.
Men are at a higher risk of OSA, with rates of 3-7% in men and 2-5% in women. (Many people with sleep apnea do not realize they have the condition, making it difficult to obtain accurate numbers.) Because of this, the majority of research on OSA and fertility has focused on men.
The regular lack of oxygen caused by OSA has been shown to reduce fertility and testicular antioxidants in male mice. Sperm were less mobile and more likely to be impacted by oxygen stress, but sperm levels did not appear to be affected.
Erectile dysfunction is also a well-known symptom of OSA, appearing in 10-60% of men with the condition. As OSA-related erectile dysfunction is caused by blood vessel cells no longer sending the correct signals, treatment of the underlying cause is crucial. While not necessarily a long-term barrier to fertility, erectile dysfunction (and other forms of sexual dysfunction) are still considered to have an impact on fertility levels and the likelihood of pregnancy.
OSA may be partially caused by (or influence) androgens, also known as “male” hormones. Androgens are present in women, but ordinarily at lower levels and with more subtle effects. The connection between androgens and OSA would explain why women with PCOS are at a higher risk of developing OSA.
Luckily, OSA can be treated effectively. Treatment usually involves the use of a continuous positive airway pressure (CPAP) machine during sleep to keep the airways open during sleep. CPAP therapy has been shown to alleviate OSA-related erectile dysfunction. It also decreases prolactin levels in women. As people with PCOS are known to have increased prolactin levels, there is hope that treatment of OSA may aid in the treatment of infertility caused by PCOS.
As discussed earlier, circadian rhythms are the “inner clock” which regulate a wide range of effects in our body, including hormone production and our sleep-wake cycle. Circadian rhythm disorders (CRD) are just as complex. They include:
What all these disorders have in common is that they describe a kind of circadian rhythm dysregulation. One way to describe these disorders is that sufferers live with a kind of permanent or semi-permanent “jet lag” when compared to the rest of the population. In fact, jet lag is itself considered a (temporary) circadian rhythm disorder.
There are few statistics on the prevalence of CRD. However, nearly a third of night workers meet the criteria for shift work sleep disorder, and delayed sleep-wake disorder is the most common circadian rhythm disorder treated by sleep specialists.
No matter which CRD an individual suffers from, it may have an impact on their fertility. We know that night-working women show altered reproductive cycles, that the circadian rhythm has a major effect on hormone levels (particularly melatonin), and women who suffer from CRD are more likely to have poor reproductive outcomes. So, although we do not yet know the full effect of CRD on fertility, the connection is clear.
While research has indicated a circadian rhythm component to male fertility, the majority of CRD-related fertility research has centered on women. This focus continues past conception, and some studies have found that babies born to shift-working mothers had significantly lower birth rates when compared to the children of mothers who worked during the day.
Treatment for circadian rhythm sleep-wake disorders differs depending on the disorder in question. Light therapy, behavioral therapy, and doctor-prescribed melatonin supplements are all common treatments and can contribute to a far healthier sleep-wake cycle.
Insomnia can be short-term (lasting under three months) or chronic (lasting over three months), and can indicate sleep-onset insomnia (difficulty falling asleep) or sleep-maintenance insomnia (difficulty staying asleep). Whatever form it takes, insomnia is the most common sleep disorder, affecting some 60 million Americans. 40% of women and 30% of men will experience insomnia in their lifetime.
Like infertility, insomnias can be caused by a wide range of biological, mental, environmental, and lifestyle factors. Everything from anxiety, to blue-light exposure, to medication, to underlying disorders can cause forms of insomnia.
In terms of insomnia’s relationship with infertility, the cause is less important, unless it is due to an underlying issue with its own effect on fertility. (Infertility can also be the cause of insomnia itself, as anxiety and depression are common among infertile couples and are known to cause or worsen insomnia.)
Women with insomnia have been found to struggle with infertility at rates four times those of women who sleep normally. This was true even when controlling for age, weight, and health complications, but the chronic health problems associated with insomnia can also have their own impact.
One theory to explain insomnia’s impact on fertility is that it has to do with the immune system. Sleep loss is known to increase inflammation and suppress the immune system. One of the markers used to measure these effects is also seen at high levels in women with unexplained infertility, indicating a possible relationship.
The treatment of insomnia is highly dependant on the individual. Cognitive behavioral therapy, medication, lifestyle changes, and other therapies can be used individually or together. Since insomnia can be caused by so many factors, it’s crucial to understand the basis of your own insomnia in order to treat it effectively.
Sleep hygiene refers to your bedtime habits and rituals. Each person has their own sleep routine, but good sleep hygiene starts with going to bed at a set time every night and then supporting sleep with healthy routines, lifestyle changes, and a bedroom set up to encourage high-quality sleep.
Along with the treatment plan suggested by your medical team, there are techniques you can use to improve your sleep health whether or not you suffer from a sleep disorder.
Fertility is a complicated process which can be impacted by many different elements. Although the relationship is not yet fully understood, it’s clear that sleep is one of those factors.
We hope this article has helped you understand the ongoing research into this topic, as well as steps you can take to improve the quality of your sleep. It’s important to remember that effective treatments are available for sleep disorders. Speak to your doctor about any concerns you have about your sleep health. Not only will you sleep better, but your care team will have a clearer picture of your fertility journey.
Whether or not you struggle with infertility, sleep has a profound impact on your life. Learn about sleep and how to improve your sleep quality by following and reading the links below: