Did you know that men and women experience sleep disorders differently, and their treatments should not be the same? This is according to new research that delves into the biological aspects of sleep across the two sexes.
Men are more prone to obstructive sleep apnea, while women are often victims of insomnia and tend to report lower sleep quality. These findings are from a literature review published in the journal Sleep Medicine Reviews. The researchers involved came from notable institutions such as Harvard University, Stanford University, and the University of Southampton in the U.K.
The research is as much about precision medicine as it is about sleep disparities between the sexes, according to coauthor Renske Lok, PhD, a postdoctoral fellow at the Stanford Center for Sleep and Circadian Sciences.
“We’re trying to move away from the one size fits all,” Dr. Lok tells Fortune. “[Medicine] needs to be more tailored.”
Women in Biomedical and Behavioral Research
Understanding how and why biological sex impacts various sleep disorders is a crucial step toward individualized treatment. However, the long-standing lack of inclusion of women in biomedical and behavioral research is a barrier. Only since 2016 did the National Institutes of Health require studies to account for sex as a biological variable.
“The biggest finding is that we absolutely have to do better in including women in our research designs,” Dr. Lok says. “Historically, women have not been included as much as men, in part because it was always assumed results from men would translate automatically to women. And we’re starting to find out more and more that this is not the case.”
Sex and Circadian Rhythm
Circadian rhythms are the mental, physical, and behavioral changes your body experiences in a 24-hour period. Almost all your organs and tissues have their own rhythms, forming a kind of master biological clock that’s particularly sensitive to light and dark.
At night, your brain produces more of the sleep hormone melatonin, which makes you feel tired. A study reviewed by Dr. Lok and her colleagues found that women secreted melatonin earlier in the evening than men. This aligns with other research showing men typically are later chronotypes; that is, they go to bed and wake up later than women. As such, men tend to have worse social jetlag, when their biological clock doesn’t align with the traditional timing of societal demands, like working a 9-5 job.
Work-life Stress May Influence Women’s Insomnia
Insomnia is about 1.5 times more common in women, previous research has shown. Dr. Lok and her colleagues theorized this may be due to certain risk factors more prevalent in women, such as anxiety and depression.
Dr. Eric Sklar, a neurologist and medical director of the Inova Sleep Disorders Program in northern Virginia, treats insomnia as one of the most common sleep disorders. “There is a high correlation with underlying psychiatric disorders and insomnia,” Dr. Sklar tells Fortune. “Some of the underlying societal stressors for men and women may be different.”
Why Do Men and Women Sleep Differently?
Women did catch a break with one common sleep disorder: obstructive sleep apnea, when the upper airway becomes blocked repeatedly during sleep. The disorder is almost three times as common in men, however, it’s only associated with an increased risk of heart failure in women, the review noted.
“It is well known that men are at a higher risk,” Dr. Sklar tells Fortune, adding that biological sex is used in sleep apnea risk assessment. “Men tend to have larger necks, and neck size is also a risk factor.”
Sleep Differences Between the Sexes
Dr. Lok’s review also highlighted these sleep differences between the sexes:
- Men have worse social jetlag.
- Women experience insomnia more frequently.
- Obstructive sleep apnea is almost three times as common in men.
One key factor remained inconsistent across the nearly 150 studies Dr. Lok and her colleagues analyzed: women’s menstrual phases. Menstruation correlates to numerous changes that impact sleep, such as elevated body temperature during the luteal phase of the cycle. Some research failed to consider subjects’ oral contraception usage, which may have skewed results.
In some instances, “we’re not sure if there are any sex differences because, simply, nobody has ever looked at it,” Dr. Lok says. “At the same time, it’s a very encouraging article because it definitely identifies where the gaps are still present.”
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