Sleep patterns, disorders differ between women and men

These and other major sleep differences are highlighted in a new review of ongoing research into sleep and gender and have implications for how women and men could be treated for sleep-related disorders. The review by researchers at the University of Southampton, Stanford University and Harvard University is published in Sleep Medicine Reviews.

“Depending on your gender, should you get a different kind of treatment or a different kind of medication or a different dosage of medication, for example,” said Renske Lok, a postdoctoral scholar in psychiatry and behavioral sciences at Stanford University who led the review.

An estimated 50 million to 70 million Americans have chronic or ongoing sleep disorders, according to the National Institutes of Health. And 1 in 3 adults in the United States experience sleep deprivation, according to the Centers for Disease Control and Prevention.

Women say they have lower sleep quality

The review found that women are more prone than men to lower sleep quality, which is associated with anxiety and depressive disorders.

The quality of women’s sleep in terms of the amount of deep sleep and the time they’re sleeping, as measured by brain activity, is good. But women complain far more than men about insomnia, the researchers found.

“Women maybe are a bit more open about … psychological consequences and the fact that they have bad sleep, whereas men are more inclined to keep it to themselves,” Lok said.

A study in 2021, not included in the review, suggested a different reason. Researchers at Lausanne University Hospital examined the sleep patterns of women to try to understand why they complained of waking up throughout the night when the sleep metrics showed they’d had a good night’s sleep.

Researchers glued 256 electroencephalographic or EEG electrodes to the scalp and face to get a deeper read on brain activity during sleep. They then woke the women at different times of night and asked them if they felt they were asleep or awake.

They found that the women who felt they had been awake frequently during the night, even though they appeared to have been asleep, were experiencing a high-frequency almost wake-like brain activity in a small part of their brain, while the other 95 percent of their brain was resting. This activity is not detected in standard sleep studies where only a handful of electrodes are used.

“Now we know that we understand what they’re feeling, because we see that in this small part of the brain, they still have some activity that makes them aware of being here, even though 95 percent of the brain is resting,” said Raphael Heinzer, director of the Center for Investigation and Research on Sleep at Lausanne University Hospital in Switzerland. “We never make fun of our patients, but we didn’t believe them.”

Women have an earlier circadian rhythm

Sleep disorders such as insomnia in women may also be because their circadian rhythm tends to run faster and begin a bit earlier in the day than that of men. A woman’s cycle is 24.09 hours, plus or minus 0.2 hours, while a man’s cycle is 24.19 hours, plus or minus 0.2 hours.

While the discrepancy may seem small, the cumulative effect over days, weeks or months could lead to a misalignment between the internal clock and external cues such as light and darkness, which may cause sleep disruptions.

The earlier cycle for women corresponds with an earlier timing in the secretion of melatonin and cortisol, researchers said. Melatonin is a natural hormone that signals to our bodies that it is time to sleep.

This finding relates to what earlier studies have found, said Christian Cajochen, head of the Center for Chronobiology at the University of Basel, who was not involved with the review. For instance, circadian rhythm differences — associated with hormones secreted during puberty — may explain sleep differences among younger men and women.

After they get their period, girls start going to sleep a cumulative 20 minutes later every year until they hit their early 20s, right about when puberty is ending.

Males experience a similar phenomenon in their teens, but it doesn’t end until their late 20s, said Cajochen, whose research includes age-related changes in the circadian regulation of sleep.

When children are sleeping and waking up “later, later, later, later, and then there is this tipping point, that’s the end of puberty. And this occurs later in men than in women,” Cajochen said. “When you see in your kids that they’re starting to get earlier again, so there is hope that puberty is over.”

Men’s risk of sleep apnea and Type 2 diabetes

The review found that men, because of the way their upper airway is constructed, are three times more likely to develop sleep apnea, making them more susceptible to health problems such as high blood pressure, diabetes, heart disease and stroke.

Also, men tend to overeat more than women when they are sleep deprived, the review found. And among shift workers, who are considered to be sleep deprived because of their unusual schedules and thus are out of alignment with their natural circadian rhythm, both men and women have a higher risk of Type 2 diabetes, but the risk was much higher in men, the researchers noted.

Gender differences are important

With such profound health implications, there is a need for better understanding about the gender differences in sleep and circadian biology, researchers said. And yet historically, biomedical research on sleep didn’t even include women, because it was thought that hormonal events such as menstruation and menopause presented so many confounding variables as to render the research unhelpful, Lok said.

If women were included, researchers typically only used women who were at the same spot in their menstrual cycle, or those who were taking oral contraceptives because they suppress the normal ovarian cycle.

The prevailing opinion was that sleep patterns were basically gender neutral, Lok said. But new studies have shown distinct differences in sleep quality, duration and latency between men and women and that these discrepancies may be caused by differences in the genders’ circadian rhythms, and the physiological changes that accompany them, such as core body temperature and melatonin levels, she said.

“In general, women have just been excluded,” Lok said. “And it’s been more or less assumed that results found in men translate to women, and we now more and more start to understand that that is not completely true.”