After women were excluded from sleep studies for decades, science is starting to catch up—and changing valuable statistics with it.
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After surgeons smoothly operated on Shirley Gabre’s right knee, nervous nurses buzzed around the edges of her convalescence. Although the procedure had gone off without incident, her postoperative oxygen levels remained far too low. She was struggling to come out of sedation and to breathe on her own again.
Gabre, who lives in Westlake, Ohio, hasn’t actually spent an entire day breathing without assistance in almost a decade. The 66-year-old, recently-retired legal secretary lives with sleep apnea, a disorder that causes a person’s breathing to stop and start throughout the night. To counteract that and keep oxygen flowing abundantly to her brain, Gabre dozes off each night with a mask secured over her nose and a piped-in connection to a CPAP (continuous positive airway pressure) machine—a bedside box that ensures the pressure in her upper airway is greater than the atmospheric pressure here on Earth. Without it, her airway would collapse at night.
Living with sleep apnea is a known risk factor for bringing on complications with general anesthesia—although, despite how patients and doctors may sometimes colloquially refer to it, being anesthetized is physiologically closer to being in a coma than “going to sleep”—so patients who may have the disorder are often screened for it prior to surgery to help manage the outcomes. But Gabre fell through the cracks, not looking the part of the sleep apnea sufferer captured in the collective imagination: an overweight, middle-aged man.
“My husband finally told them, ‘You know, she’s on a CPAP machine. If you put that on her, it might help,’” Gabre recounts. And it did. But without her partner’s advocacy, she could have suffered major respiratory, cardiovascular, or neurological trauma simply because women are often overlooked for sleep apnea and its related risks.
That’s something that’s finally changing. An emerging body of research links sleep apnea to biological sex, aging, and hormonal status, showing that as women approach menopause, they become increasingly likely to develop this chronic sleep disorder. The studies could not only lead to a better understanding of sleep apnea but also menopause itself, and they could rectify decades of basic biomedical research that excluded female bodies, a blindspot that today’s patients, like Gabre, still feel the effects of.
Staying on the Surface
Menopause is a biological transition as significant as puberty, just at the other end of life: it marks the end of recurring menstrual cycles that a natural decrease in the hormones estrogen and progesterone cause between the ages of 45–60. Despite the significance of this change, the fact that about half the global population will experience it in their lifetime, and that some will spend about one-third of their life in this phase, menopause is incredibly understudied and poorly understood outside of its impact on reproduction.
Research over the last 30 years has increasingly shown links between menopause and serious system-wide health issues such as heart disease, stroke, and osteoporosis, but there remains little information about exactly how these outcomes are all connected. It can’t all relate back to estrogen because hormone-replacement therapy—the only available medical treatment for menopause, which relies on a renewed influx of estrogen—only abates the most surface-level symptoms of menopause, such as hot flashes or vaginal dryness. The stakes are also quite high for this treatment, perhaps outweighing its limited benefits: the blast of estrogen can open the door to even bigger problems like breast cancer.
As long as the basics of menopause continue to be misunderstood, so will any domino effects it begets, including an increased likelihood of developing sleep apnea.
Across the population, about two percent of women carry a diagnosis for sleep apnea, compared with four percent of men, but the Society for Women’s Health Research estimates that the reality is more like one in five women have sleep apnea—90 percent of whom have no idea it afflicts them. But all of these numbers are averages, across all age groups. For women, sleep apnea status increases with age and changes in hormone levels. In a longitudinal study in Canada, conducted among more than 6,000 women, 10.4 percent of those who were pre- and perimenopausal screened positive for obstructive sleep apnea—the most common type of sleep apnea—compared with 14.6 percent of postmenopausal women.
When Gabre first entered a sleep study, seeking answers for her chronic exhaustion, she was perimenopausal—and snoring so loudly she at times would wake herself up (as well as her husband, much to his chagrin). She had enough trouble breathing that a physician recommended she begin using the CPAP machine that ultimately helped bring her out of sedation after her knee surgery, but she didn’t yet rate a positive screening for sleep apnea. That would take another 10 years, by which point she was postmenopausal. Gabre says that her mother and four sisters also all have sleep apnea and sleep with assistance from CPAP machines.
It can take some women more than 20 years to get diagnosed, if at all. Menopause generally wreaks havoc on sleep, but because it remains such a poorly understood biological event, women who report extreme tiredness are often brushed off as merely struggling from the disruption of nightly hot flashes, rather than something more life-threatening. Some women are also misdiagnosed as having exhaustion tied to depression (in reality, depression is actually a comorbidity of sleep apnea, but only one of the twin disorders gets noticed).
Getting Left Out
Despite the strong statistical links between menopause and sleep apnea, scientists still only have a very fuzzy understanding of the role that shifting hormones seem to play in exacerbating this disorder. Leading sleep researcher, Julie Carrier, who was involved in the longitudinal Canadian study, says that for decades researchers only conducted sleep apnea studies on men, and excluding women specifically because of their menopausal status, an ongoing issue throughout biomedical research.
In the case of studying sleep apnea specifically, Carrier says that researchers felt women’s fluctuating hormones made them a hazard to sound scientific research—there were too many variables to correct for—rather than presenting an incredible opportunity to understand how late-life hormonal changes can have tectonic, system-wide biological effects beyond menstruation and reproduction. Researchers are just now trying to catch up.
“We don’t really understand why women are protected [from sleep apnea] until menopause, but we know that they are,” says Carrier, who conducts her research at the University of Montreal. “Now we have more data, but still, it’s way behind other fields of sleep.”
Although there is increasing acceptance of the basic fact that menopausal women are quite likely to experience sleep apnea, there are still only hypotheses about how this biological event opens the floodgates. One idea is that as the production of the sex hormones estrogen and progesterone decrease so too does the body’s ability to extend the airway, as it would during normal breathing, but exactly how this relationship works remains a major open question. Another hypothesis is that adipose tissue—or body fat—gets redistributed around the neck during menopause, obstructing the airway.
Although sleep apnea diagnostically centers on pulmonary function, the knock-on effects of it going untreated are widespread: the body’s failure to properly circulate oxygen can lead to debilitating cardiovascular episodes and irreversible cognitive decline that can go as far as full-on dementia. Advocating for diagnostic equity here is really a matter of life or death.
“Sleep apnea is certainly one of the most serious sleep disorders and there are more and more indications that if you don’t treat sleep apnea, it’s not a good prognostic for your brain health, long-term,” says Carrier. “But the more we’ll be talking about it, the more women will become sensitive to the possibility of suffering from sleep apnea.”
A middle-aged man, as it turns out, is not the archetypal picture of a person with sleep apnea, he’s just the prototypical one.