Although the mean prevalence of obstructive sleep apnea (OSA) in women is increasing and can approach that of men (22.5% for females, 27.3% for males) in certain populations, OSA is still widely regarded as a predominately male disorder.1 Women are less likely to be referred for sleep testing than men, even when reporting similar symptoms.2 When they are tested, women are less likely to be diagnosed with or treated for OSA, even though they often suffer a higher symptomatic burden.1
Emerging data highlights how obstructive sleep apnea in women can be incorrectly diagnosed—or missed entirely—at different stages of the journey.
"While OSA is still widely regarded as a predominately male disorder, the mean prevalence of OSA in women is increasing and can approach that of men."
Recent research is uncovering new realities about the female experience of obstructive sleep apnea, starting with quite significant differences in symptoms.
While men usually complain of heavy snoring, witnessed apneas, nocturia and daytime sleepiness, women are more likely to report non-specific symptoms such as daytime fatigue, insomnia, nightmares, depression, anxiety and gastric reflux. These symptoms of sleep apnea in women can easily be misattributed to other conditions ranging from anemia, cardiovascular disease, hypothyroidism and type 2 diabetes to depression, menopause, overwork, insomnia and hypochondria.1,4,5,6
Anecdotally, many women report that healthcare providers classify their sleep apnea symptoms as side effects of an aging body or a busy lifestyle. Other women don’t even seek help due to societal stereotypes that peg OSA as a ‘male’ disorder or consider snoring to be ‘unladylike’.3
As well as being inaccurately attributed to other conditions, obstructive sleep apnea symptoms in women can be masked by common comorbidities.
Women with OSA do have high rates of comorbidities: they are more likely to be diagnosed with cardiovascular disease, hyperlipidemia, diabetes, asthma, arthropathy and gastric reflux than women without OSA, and they have significantly higher rates of gastric reflux, depression, anxiety and asthma than men with OSA.4,5 The symptoms of these comorbidities can easily mask those caused by sleep apnea. Obesity, for example, is strongly correlated with OSA but is also independently associated with anxiety, depression and sleepiness.
Due to the limited awareness of ‘non-classic’ OSA symptoms in women and the potential for those symptoms to be masked by other comorbidities, it is unsurprising that sleep-related issues are so easily overlooked in women. The impact of sleep on overall health and the specific risks associated with untreated sleep apnea, however, mean that steps must be taken to address this situation.
Physical and hormonal differences mean that women experience both sleep and sleep apnea differently to men.
Women generally appear to require more sleep, take longer to fall asleep, and experience more slow-wave sleep than men. Their bodies respond more quickly to changes in blood gases, which results in faster activation of the sympathetic nervous system, optimized minute ventilation and faster arousal from sleep during airway obstructions.6 Before menopause, the upper airway in women is less collapsible and more stable during sleep, in part due to the modulating effects of sex hormones but also because women have smaller tongues and soft palates, shorter airways and less soft tissue around the airway. As a result, pre-menopausal women tend to experience fewer apneas than men and are less likely to snore.1
As women enter menopause, changes in hormones and fat distribution7 cause these sex-based differences to fade and OSA diagnoses in women to rise significantly: below the age of 50, around twice as many men are diagnosed with OSA, but after menopause, prevalence is almost as high in women as in men.8 Post-menopausal women also tend to report OSA symptoms that are more like those reported by men. The presence of a large cohort of women who report recognizable OSA symptoms and are diagnosed using standard methods may make it even less likely that women with female-specific symptoms will receive an appropriate diagnosis.
The standard OSA diagnostic tools and scoring system are based on the typical presentation of the condition in men. Sleep studies assess OSA and its severity using the apnea-hypopnea index (AHI), which identifies the number of apneas and hypopneas per hour of sleep. This reflects the prevalence of collapsed airways, loud snoring, gasping apneas and extended hypopneas in men, but fails to account for the fact that women frequently do not present these symptoms at all. The reliance on AHI puts female patients at a significant disadvantage and may well result in missed diagnoses.
Alison Wimms, Director of Medical Affairs at ResMed and a leading researcher in the field of women and sleep apnea, emphasizes the need to look beyond AHI when assessing potential OSA in women. “It’s not a secret in our field that we’re kind of stuck using AHI, which is potentially quite meaningless in a lot of this,” she explains. “We need to look at many other things.”4
For the anatomical and hormonal reasons described above, women with OSA typically experience lower AHI, with shorter apneas and less severe hypopneas. They experience less oxygen desaturation, more ongoing flow limitation, and more hypopneas that result in arousal before significant oxygen desaturation occurs.9,10 AHI scoring can fail to identify these events as apneas and hypopneas.
Some women also experience clusters of apneas and hypopneas during REM sleep but far fewer during non-REM sleep.11 When a patient is tested in a lab versus at home, they may be less likely to fall into REM sleep, further skewing the true picture of their sleep-disordered breathing. This may result in false negatives and an under-reporting of the severity of an OSA diagnosis; it could also explain why women suffer a disproportionately high symptomatic burden relative to their AHI score. Again, this highlights the need for a new approach to OSA diagnostics for women.
Changes to the hypopnea criteria in the American Academy of Sleep Medicine (AASM) Clinical Practice Guidelines 201212 have made scoring more inclusive of women but further work is required to ensure that testing and scoring reflects the full range of their experiences. Patient phenotyping13,14 is shedding light on the different clinical presentations, comorbidities and treatment needs of women with sleep apnea and could support a shift towards more nuanced and accurate sleep testing for women.
Sleep apnea can have a significant impact on patient health and quality of life. OSA is a treatable condition, but many women face significant and ongoing barriers to accessing diagnosis and treatment. Whether due to societal beliefs that men are more susceptible to sleep apnea, or because women are less likely to present with easily recognized symptoms, too many women with OSA go undiagnosed, untreated and without the answers and therapy they so desperately need.
Shedding light on the multiple factors that undermine women’s access to OSA diagnosis and treatment will, we hope, enable more women to receive much-needed screening, testing and therapy for obstructive sleep apnea.