The reported prevalence and severity of obstructive sleep apnea in women is lower, compared with men, but the consequences of the disease are “at least the same, if not worse,” with women appearing to have greater susceptibility to adverse OSA-related cardiovascular consequences – particularly as it pertains to endothelial dysfunction, Reena Mehra, MD, MS, said at the virtual annual meeting of the Associated Professional Sleep Societies.
Women more so than men have endothelial dysfunction associated with OSA, “suggesting there is an enhanced sensitivity of the female vascular endothelium to intermittent hypoxia,” said Dr. Mehra, director of sleep disorders research at the Cleveland Clinic and professor of medicine at Case Western Reserve University, also in Cleveland.
Sex-specific differences in the anatomic and physiological characteristics of the upper airway, in fat distribution and in respiratory stability as they relate to OSA have been documented for some time – and today, these and other differences relating to the diagnosis, treatment, and consequences of sleep apnea continue to be studied and elucidated, said Dr. Mehra, Anita Rajagopal, MD, and Chitra Lal, MD, in a session on OSA in women. Each spoke about the breath and implications of these differences, and of increasing recognition of the significance of OSA in women.
Likely underdiagnosis
Epidemiologic studies have suggested a three- to fivefold higher prevalence of OSA in men than in women in the general population. But it has also been estimated that 17%-25% of women have sleep apnea, and the prevalence reported in various studies has generally increased with time, said Dr. Rajagopal, department medical director for sleep medicine at Community Physician Network in Indianapolis, and medical director of the Community Health Network Sleep/Wake Disorders Center, also in Indianapolis.
One population-based study in Sweden, reported in 2013, found OSA (defined as an apnea-hypopnea index [AHI] ≥5) in 50% of women aged 20-70, she noted.
It’s quite possible women are being misdiagnosed or underdiagnosed because of their reporting of different symptoms, Dr. Rajagopal said. The Epworth Sleepiness Scale, commonly used to screen for OSA, has not been validated for use in women and has not been strongly associated with daytime sleepiness in women in population-based studies, she said, noting that women who report similar levels of daytime sleepiness to men are less likely to have an ESS score greater than 10.
“We shouldn’t rule out obstructive sleep apnea in women with a low ESS,” Dr. Rajagopal said in an interview after the meeting. Attentiveness to the symptoms more often reported by women – generalized daytime fatigue/lack of energy, insomnia, morning headaches, mood disturbances, and nightmares – is important, as is performance of overnight polysomnography when a home sleep study is negative and there is clinical suspicion of OSA.Respiratory disturbances in women are frequently associated with arousals – which induce less ventilatory instability in women than in men – rather than oxygen desaturations, leading to underestimation of OSA on home sleep testing. Insomnia associated with OSA in women may also increase the likelihood of a false negative result, Dr. Rajagopal said at the meeting.
“It’s really important [in sleep testing] to consider your AHI values in women,” she said. “The AHI value may not provide a true indication of the degree of sleep fragmentation being experienced by patients.” That OSA symptoms manifest in women with lower AHIs has been elucidated in research showing, for instance, that those with an AHI of 2-5 per hour have a similar level of symptoms to men with an AHI of at least 15 per hour, she said.
Women tend to have a clustering of apnea during REM sleep, and it’s possible that “the long-term effects of REM disruption contribute to greater symptomatology at lower AHI values in women compared to men,” Dr. Rajagopal said.
Also at play are when it comes to testing and diagnosis are several other key sex differences, she said. For one, the upper airways in women are less collapsible and more stable during sleep (most evident during non-REM sleep), and respiratory events during sleep are less frequently associated with complete upper airway collapse.
Women also have shorter apneic episodes, but “the longest apneas are associated with a more severe oxygen desaturation,” she said. Moreover, they have more episodes of upper airway resistance during sleep, which in and of itself “has been shown to produce clinical symptoms such as daytime fatigue and clinical depression.”
In her presentation, Dr. Mehra similarly commented on a likely underdiagnosis of OSA in women. In addition to differing symptoms, including palpitations, “women are less likely to have arousals, and have a lesser degree of nocturnal hypoxia compared to men ... perhaps leading to even more of an underdiagnosis.”