Women’s Health

When sleep is routinely interrupted, or fragmented, the sleep cycle and circadian rhythm can be disrupted. This disruption is dangerous to overall health and well-being, in the long-term and the short-term. Poor sleep quality and circadian rhythm disruption are linked to a higher risk of a wide variety of diseases and chronic health conditions, as well as to mood disorders and cognitive performance issues. In a recent McGill University study, researchers found that mothers – but not fathers – of more than one child are particularly at risk of suffering from fragmented sleep.

What the Sleep Fragmentation Study Found

Conducted by Samantha Kenny, a doctoral student at McGill University, under the supervision of Department of Educational and Counseling Psychology Assistant Professor Marie-Hélène Pennestri, the study was based on a group of 111 parents. That group included three single mothers and 54 parenting couples. The researchers tracked each group member’s sleep patterns for two weeks.

Researchers found that the overall quantity of sleep for the mothers didn’t vary according to the number of children they had. However, those with just one baby tended to have a better quality of sleep with fewer interruptions. Mothers of more than one child tended to have a poorer quality of sleep, and sleep that was more fragmented by interruptions. Interestingly, the fathers in the study experienced no change in sleep quality whether they had one child or multiple children.

Researchers Question Disparate Impact

Noting the difference in the degree of sleep fragmentation between mothers and fathers, researchers plan to delve deeper into that topic in future research. However, the researchers did point to couples striving towards a more equitable division of child-rearing tasks, during both the day and the night, as a means of reducing the mother’s greater rate of sleep interruption. Even today, women – even those working outside of the home – typically do more of the child-rearing related labor than their male partner.

This pattern of unequal division of childcare tasks can happen even in homes where a conscious effort is made to divide household chores equitably. It can often develop into a habit unintentionally, such as when the mother breastfeeds. Clearly, the father can’t breastfeed and when one or both parents have to get up for work, it doesn’t make sense to have both getting up with the baby at night when the mother is going to be doing the feeding. The problem comes when this becomes a long-standing habit, where the mother becomes habitually responsible for nighttime parenting issues.

Common Causes of Fragmented or Interrupted Sleep

While mothers of multiple children are more likely to experience disrupted sleep, fragmented sleep is a sleep problem that can impact anybody at any age, including children and adolescents. Some common causes of sleep fragmentation include stress, anxiety, alcohol or drug use, some sleep-inducing medications, daytime napping and a lack of consistency in waking and sleeping times. Sleep apnea, heavy snoring, feeling itchy or scratching a lot during sleep, periodic strong leg movements and excessive screen time, especially right before bedtime, can also contribute to interrupted sleep.

Health Implications of Fragmented Sleep

This type of interrupted sleep can be very damaging to overall health and well-being. That’s because it disrupts multiple cycles essential to optimal health, mood maintenance and cognitive functioning. Poor quality sleep is disruptive to the circadian rhythm, interferes with restorative deep sleep and has a negative impact on REM sleep. Studies have linked sleep fragmentation to hardening of the arteries, chronic inflammation and it may be a migraine headache trigger.

Routinely disrupting the circadian rhythm can interfere with the timing of various body systems, including hormone production and release, the metabolic system and the cardiovascular system. That can heighten the risk of a wide range of common diseases and chronic health conditions, including cardiovascular disease and stroke. A higher risk of developing hormone-related cancers, such as breast cancer and metabolic system diseases, including diabetes, have been associated with circadian rhythm disruption. So, too, have mood disorders, including anxiety and depression, and cognitive function impairment, such as decreases in memory and complex task performance.

REM sleep is also important to cognitive function and memory consolidation. Deep sleep is essential to immune system function, tissue and bone repair and growth and cell health. Quality sleep, meaning completing the sleep cycles of a good night’s sleep, is essential to better mental health and cognitive function, including memory and the ability to learn and retain information. Disrupted sleep patterns can contribute to cognitive decline in the elderly.

Make Time for Quality Sleep

Getting enough quality sleep is a major factor in short-term and long-term health and well-being. It can be tempting to let social, work and extra-curricular school activities eat into available sleep time or to fall into old patterns of childcare that leave one partner struggling with the bulk of nighttime sleep interruptions. Be conscious of the health consequences of insufficient, interrupted and poor quality sleep. Prioritizing good sleep hygiene for all family members, including mothers, is a smart way to help keep the whole family healthy.

While male fertility is relatively straightforward, female fertility is governed by complex systems. The hormone levels of a fertile woman change by the day and even by the hour. Although we know a great deal about how monthly cycles affect female fertility, new research suggests that daily cycles, also known as the circadian rhythm, may also play a role.

The Cycles of Female Fertility

Women’s fertility is controlled by a complex system of internal clocks. Most fertile women have a monthly cycle that is roughly 28 days long. The first day is the day when menstruation begins. Two weeks later, most women ovulate and are fertile for just a few days. Levels of the hormones estrogen, progesterone, LH and FSH fluctuate widely to keep this internal clock on track.

Although these monthly cycles are important, there is evidence that our daily circadian rhythms also play a role. Understanding this connection may be an important part of solving the very common problem of female infertility.

Links Between Circadian Rhythms and Fertility

How does a dysregulated circadian rhythm affect fertility? While this is still a new area of study, it is clear that our sleep-wake cycles are as important as our monthly cycles in maintaining the ability to reproduce. Shift workers, or people who work unusual hours, are more likely to have menstrual issues and more than ten percent more likely to suffer from infertility.

In addition, there is a matter of proximity. The suprachiasmatic nucleus (SCN) of the brain controls our internal clocks. It also is responsible for controlling the release of LH, the hormone that signals the ovaries to release an egg. In addition, our ovaries appear to be partially controlled by Clock genes, which are the gene group most important in regulating circadian rhythm. As a result, LH is at its highest levels early in the morning.

Is this correlation a coincidence or proof of our circadian rhythms affecting fertility? Several new studies suggest the latter. In one experiment, scientists mutated the Clock genes of mice in a laboratory. Without any other changes in their environment, the mice began to have disrupted hormone levels, ultimately leading to lower fertility. Even plants appear to have some relationship between their circadian rhythms and fertility.

This link between sleep-wake cycles and fertility makes sense on an intuitive level. We are more likely to become pregnant if the hours of highest fertility occur at a time when we are awake. Evolution likely has affected the female body by helping women to ovulate when they are also more likely to find a partner. However, this effect has only been noted in women. While the ovaries express Clock genes, the testes do not.

The Bottom Line on Sleep and Reproduction

Getting enough sleep is crucial to maintaining good health. This is especially true if you are trying to conceive.

Women who have sleep apnea and other sleep disorders are three times as likely to experience infertility as women who have healthy sleep habits. In addition, women who are undergoing IVF and other fertility treatments have a higher chance of getting pregnant if they are getting seven to eight hours of high-quality sleep. If you are trying to get pregnant, getting plenty of sleep and keeping your circadian rhythms on an even schedule may increase your chances.

Although male fertility does not appear to be as affected by sleepless nights, it is still important for men to keep their sleep-wake cycles on a balanced rhythm. Not getting enough sleep is associated with lower sperm counts and also a lower sex drive in men, making sleep very important for their sexuality and ultimately their fertility.

Sleep: Crucial for Whole-Body Health

Whether you are trying to conceive or not, maintaining good sexual health is an important part of living a happy and fulfilled life. However, many modern people have lifestyles that make this difficult. If you are struggling to get the sleep you need, consider making the following changes to your daily routine:

• Keep a set daily schedule, sleeping, waking and eating at roughly the same times of the day.
• Expose yourself to plenty of bright light throughout the day while dimming lights (and smartphones!) at night.
• Use blackout curtains to reduce light pollution if you live in a heavily populated area.
• Keep a bedtime routine that helps you to feel relaxed when you climb into bed.
• Consider trying a melatonin supplement if you struggle to fall asleep even after making the above changes.

Getting enough sleep is important for your fertility, but more so for your overall health. If you want to live the healthiest and happiest life possible, keeping a steady circadian rhythm is an important lifestyle change.

Our circadian rhythm helps to set our daily cycles, determining when we wake and sleep. However, recent studies suggest that our circadian rhythm and other internal clocks are more important to whole-body health than previously known. The circadian rhythm has an effect on digestion, our immune systems and even cardiovascular health. According to new research on how circadian clocks in the ovary function, internal clocks may also affect fertility and reproduction.

The Monthly Rhythm of Female Fertility

While male fertility is fairly straightforward, female reproductive cycles are complex, with hormonal levels varying by the day and even by the hour. Every monthly cycle is made up of three distinct phases. The first phase is called the follicular phase and is spread over roughly the first fourteen days of the cycle. In this phase, the follicles in the ovaries mature in preparation for the second phase, ovulation. The hormones LH and FSH spike to induce the egg to be released just before ovulation.

After ovulation comes the third phase, the luteal phase, which lasts approximately the last two weeks of the ovarian fertility cycle. In this phase, the body releases hormones to support an early pregnancy, should one have occurred, including high levels of the hormone progesterone. If no pregnancy occurs, progesterone drops sharply and menstruation begins, with the cycle beginning anew once again.

Clearly this monthly rhythm is extremely important for the continuation of the human race. However, new research suggests that daily, or circadian, rhythms also are important in helping to support female health and fertility.

Circadian Clocks in the Ovary and Fertility

Scientists have long suspected that there is a link between circadian clocks and fertility. Part of this is due to the mere proximity of the two mechanisms, as both functions are controlled by the same area of the brain. In addition, shift workers have been shown in several studies to have a higher incidence of infertility and other reproductive disorders.

However, there have been other scientific hints that sleep and female fertility are linked. More than 50 years ago, researchers noted that female rats experienced certain monthly hormonal surges in the afternoon. In addition, laboratory animals have been shown to be less fertile when subjected to changes in circadian rhythm, such as being on a sleep-wake schedule that spans less than 24 hours. Several new studies have shed light on this topic, suggesting that circadian clocks in the ovary may be more important to fertility and reproduction than previously known.

Two-Way Communication Between Sleep-Wake Cycles and Fertility Clocks

In a recent study, researchers took several groups of mice and stopped the functioning of certain genes that are known to control circadian rhythm, such as CLOCK and BMAL1 genes. When they deleted these genes, there was a predictable change in the release of reproductive hormones. For example, when one gene was deleted, the mice being studied all had hormone surges occur two hours earlier than previously.

However, communication between circadian clocks and fertility hormones is not one-way. A different study suggests that luteinizing hormone (LH), a hormone that induces ovulation, also helps to set circadian clocks, especially the clocks located in ovarian tissue. The exact relationship between circadian rhythm and fertility has yet to be determined, but it is clear that these two systems interact with each other.

What Happens When Clocks Are Off?

Circadian rhythm disorders are incredibly common. This new research brings up the question: What happens to reproductive cycles when circadian clocks are awry? The researchers who performed the recent studies on circadian clocks and fertility in mice note that the small changes in fertility hormones seen in mice with circadian gene deletions often left the mice less fertile or even totally unable to reproduce. Although humans are not mice, our systems are similar enough to raise suspicion that women with sleep disorders may not be as fertile as they could be.

Although circadian clocks appear to be important in female fertility, this does not mean that they play a similar role in male reproduction. On the contrary, male reproductive organs do not seem to have as strong of a connection to timing and internal clocks. Although men can experience a variety of negative effects when their circadian rhythm is off time, there is no evidence to suggest that their fertility takes a hit.

Circadian Rhythm Affects Every Area of Health

The modern world is not conducive to keeping internal clocks ticking along. However, your circadian rhythm is crucial to your health in a variety of ways. If you are not getting the sleep you need or keeping a regular sleep schedule, nearly every system in your body will be affected. As we are seeing in several recent studies, your internal clocks influence more than we previously could have imagined.