The purpose of this article is to provide an overview of known similarities and differences between genders relative to presenting symptoms, demographics, and severity of obstructive sleep apnea. There is a relationship of risk of disease occurrence relative to stages of reproductive life of a woman, indicating that chronologic age might not be as important as timing of pregnancy and menopausal transition. The current understanding of gender differences in treatment success and compliance with oral appliance therapy is limited and requires further investigation.
Key points
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Women with sleep apnea are often unrecognized owing to differing symptomology.
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The prevalence of women with obstructive sleep apnea increases with age but more specifically with the menopausal transition.
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There is a lack of gender difference in bruxism and risk of obstructive sleep apnea with bruxism.
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Oral appliances seem to have more successful outcomes with women than men.
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There is a tremendous need for more research in the area of gender-specific indications and outcomes with oral appliance therapy.
Introduction
Obstructive sleep apnea (OSA) is characterized by repetitive upper airway collapse during sleep. This condition can lead to a complete cessation of breathing for 10 seconds or more (apnea) or partial collapse of the airway, resulting in either an arousal or oxyhemoglobin desaturation exceeding 3% (hypopnea). The resultant effect of this decreased airflow is episodic oxygen desaturation, sleep fragmentation, and marked negative intrathoracic pressures. In the past, sleep-disordered breathing (SDB) with symptoms of snoring and sleepiness were viewed as comical by others, an embarrassment for the individual, and an annoyance for the sleep partner. However, a multitude of studies have proven that OSA over time can negatively impact cardiovascular and metabolic health and is associated with hypertension, type II diabetes, myocardial infarction, coronary artery disease, stroke, heart failure, pulmonary hypertension, and arrhythmias. It can also lead to a lack of concentration and insomnia and contribute to psychiatric disorders such as depression. At present, OSA is recognized as a major public health issue on a global scale, the prevalence of which is increasing owing to the obesity pandemic, the aging of our society, and improvements in screening and testing methods. In the United States alone, the number of people affected with untreated SDB is approximately 12 to 18 million adults and this number is increasing.
SDB has traditionally been assumed to be a condition occurring in men. The stereotypical overweight, snoring, middle-aged, sleepy man was an easy identifier to clinicians and led to easy identification of cases for further screening or evaluation. Epidemiologic studies using population samples free of clinical selection bias have raised our awareness of the magnitude of this condition and the presence of many subgroups of individuals with remarkably disparate presentations.
Relevant to this review, it has been suggested that the prevalence of symptoms and conditions associated with OSA can vary according to gender. Women who do not present with the classical clinical picture of the syndrome (loud snoring, witnessed apneic events, daytime sleepiness, obesity) might not get referred for screening for OSA and suffer the consequences of this condition unnecessarily. Ultimately, the recognition of gender differences in symptoms and associated comorbidities could improve screening and early diagnosis. Before 1993, women with SDB were not reported in the literature simply owing to a lack of awareness that this condition could exist in the female population. This lack led to many women suffering from this condition owing to the lack of a diagnosis. Young and associates were the first to include women in a large study of prevalence of OSA syndrome (OSAS) in a general population sample. Over the past 2 decades, this knowledge deficit is slowly being filled with research found in sleep medicine publications, yet this area of study remains underrepresented. Furthermore, information is relatively absent in the dental sleep medicine literature and is the basis for the presentation of this review.
Gender differences in the prevalence of obstructive sleep apnea
Sleep apnea is measured with a home study or overnight sleep study (polysomnogram) by a qualified sleep physician and is a requirement for proper diagnosis and treatment. The total number of apnea, hypopnea events divided by total sleep time in hours observed in the study yields the apnea–hypopnea index (AHI). A diagnosis based on AHI is shown in Table 1 .
| Severity | Grading |
|---|---|
| Mild OSA | AHI ≥5 and <15 per hour of sleep + symptoms or comorbidity factors |
| Moderate OSA | AHI ≥15 and <30 events per hour of sleep |
| Severe OSA | AHI ≥30 events per hour of sleep |
In the landmark 2009 Wisconsin Sleep Cohort Study, of the 352 men and 250 women, 30 to 60 years of age, 24% of the men and 9% of the women were found to OSA measure at an AHI 5 or greater. OSAS is defined as OSA plus excessive daytime sleepiness occurred in 4% of men and 2% of women. Since then, a review on the epidemiology of sleep apnea revealed that an AHI of 5 or greater occurred in population-based studies at a mean frequency of 22% in men and 17% in women. Wide variation in the prevalence was noted in the various studies, which could be due to the heterogeneity in the diagnostic criteria used for AHI and the age and sex of the study population.
What is intriguing is that, although this higher risk in men stays consistent in the elderly population, the prevalence in both genders increases markedly. For example, comparing the prevalence of OSA in a general population ages 40 or older to less than 60 versus 60 years or older, it was found that the younger age group was positive for OSA in 11.7% of men and 4.3% of women, and this finding increased to 21.1% of men and 10.8% of women in the older age groups. This study was conducted in Switzerland on an exclusively white European population with a low prevalence of obesity and could possibly portend a higher prevalence in an American population. However, this study highlights not only the surprisingly high prevalence of this condition in the population, but also the remarkably close ratio of prevalence of SDB in men and women, which ranges between 2.7:1.0 in the middle-aged population to 2:1 in the older aged groups. Both these ratios show much greater risk in women than ratios found in earlier studies of 9:1.
Prevalence according to menopausal transition
The increase in sleep disturbances with age in women has been studied according to stages of menopause. In the perimenopausal period, there is an increase in sleep fragmentation, increased awakenings, and poorer sleep quality. Chronic insomnia may develop in as many as 31% to 42% of perimenopausal women with increasing prevalence in the later stages of perimenopause. In addition, the rates of occurrence of mood disorders, such as depression, can double during the menopausal transition, independent of other known factors. With transition from premenopause to postmenopause, the severity of SDB as measured by AHI, increases independent of chronologic age and body size. It is suggested that there is an exposure–response model between time in menopause and degree of severity of AHI. Interestingly, the prevalence of OSA is decreased in menopausal women on hormone replacement therapy, suggesting a hormonal effect on risk for sleep apnea independent of age and body mass index (BMI).
The time period of pregnancy has a widespread association with poor sleep quality, frequent awakenings, and nocturia. However, what is less commonly known is that distinct changes in sleep characteristics occur between the first and third trimesters. Not only are there shorter sleep durations, more awakenings, poorer sleep efficiency, and less REM sleep in the late stages of pregnancy, but there is an increase in the severity of sleep apnea and periodic limb movements. Risk factors for SDB during pregnancy are high BMI and more advanced age. It has been demonstrated that SDB during pregnancy increases a woman’s vulnerability to pregnancy-induced hypertension and gestational diabetes.
Because the consequences can be serious for untreated SDB in the pregnant woman, our awareness should be heightened. However, the current screening tools for SDB are not targeted to the pregnant population and can have poor predictive ability. Improvement in screening tools and awareness among all providers treating this population needs to occur to better identify and manage maternal and fetal well-being.
Gender differences in the clinical presentation and severity of the condition
Clinical Presentation
People initially seek treatment because of the symptoms associated with OSA. Although we are familiar with the presenting complaint of snoring and witnessed apneic events, there are many other night time symptoms that can disrupt sleep and contribute to overall sleep quality. Additionally, there are many daytime symptoms associated with SDB. People with symptoms of sleep problems are at a higher risk of motor vehicle accidents, reduced work productivity, reduced socialization, and reduced overall quality of life as compared with the general population. It is believed that the diagnosis of SDB in women is often missed because the clinical presentation is different than the traditional presentation first identified predominantly in men, and women underreport their symptoms.
These female-specific symptoms and medical comorbidities associated with SDB could lead to reduced recognition of risk for SDB and lack of referral to a sleep specialist for sleep testing. Thus, it is important to understand the gender-related differences in symptoms and increase our recognition of risk of OSA in women and potentially develop better screening tools in our history and examination.
Demographic
Obesity is more prevalent in female patients with OSA, especially those in perimenopause. An average BMI of 36 for women compared with an average of 32 for men was found in 2 studies. A statistically significant difference in age was found with female OSA patients being older.
Comorbid Conditions
Hypertension, diabetes mellitus, thyroid disease, and asthma are reported to be more common in women as are insomnia and depression. Gastroesophageal reflux disease has a higher prevalence in those diagnosed with primary snoring and OSAS, regardless of severity, as compared with the general population. Although in 1 study by Basoglu and colleagues study there was no gender preference found, in another study Hesselbacher and colleagues found a significant increase in female patients with OSAS patients gastroesophageal reflux disease, necessitating further investigation.
Sleep Bruxism
The prevalence of bruxism among middle-aged patients is estimated to be 6.0% to 8.6%. However, the method of diagnosis ranged from self-report to practitioner opinion, which lack sensitivity. The gold standard in the diagnosis of bruxism is polysomnography. The association between sleep bruxism and OSA has been studied by several authors. In 1 study, 30 patients diagnosed with a worn dentition received a polysomnogram. Of these patients, 93% tested positive for sleep apnea suggesting a relationship between sleep bruxism and OSA. This positive association has been shown in other studies as well. Although an association does exist between bruxism and OSA, there is no evidence showing a higher prevalence of bruxism in women. It is interesting to note that sleep bruxism peaks in the premenopausal years of 45 to 54, and yet the mean age of diagnosis of OSAS in women is 56, further distancing a potential relationship between sleep bruxism, OSA, and gender. More extensive studies need to be done in this area to validate this association as well as to determine the pathophysiology of OSAS and sleep bruxism.
Temporomandibular Disorder
A positive correlation has been found between temporomandibular disorder and OSA. There is no evidence to show an increased correlation of temporomandibular disorder and OSA in the female population. However, the current evidence raises the question of improvement in screening for OSA risk in our current population with temporomandibular disorder.
Severity of Obstructive Sleep Apnea
In studying the severity of sleep apnea by gender, it is apparent that women tend toward milder forms of sleep apnea than men. It was also found that their apneic episodes were shorter than those in men, and that they had a higher occurrence of partial airway collapse. Mohsenin found that women were almost twice as likely to have primary snoring as OSAS. Conversely, men were almost 3 times more likely to have OSAS as primary snoring. Epidemiologic studies have reported on the higher prevalence of women with mild OSA with AHI of 5 or greater as compared with moderate OSA with AHI of 15 or greater. The risk of presence of OSA increases dramatically to 68% when combining factors of a BMI of 40 or greater and age greater than 50 in women.
Symptoms
There is a growing awareness of symptom differences by gender and degree of severity of these symptoms. Without knowledge of these differences, underrecognition of OSAS can occur, leading to a lack of referral to a sleep clinic for laboratory or home study evaluation. The classical symptom presentation of a patient with a partner complaint of witnessed apneas is specific to men. Women present more commonly with excessive daytime sleepiness and daytime fatigue, insomnia, and sleep fragmentation. However, daytime sleepiness as a standalone symptom does not seem to be a good differentiator between males and females positive for SDB.
Females referred for a sleep study present more often than males with headaches. The odds ratio male to female is 1.0:2.7 for headaches. Shepertycky and colleagues found that the main presenting symptom for women was insomnia, not witnessed apnea. Unfortunately, the risk is that these presenting symptoms are believed to be associated with depression and do not lead to an evaluation for OSA.
In the literature, an opinion has been formed that there are female distinctive symptoms of OSA as well as some that are not gender specific. An overview of the literature revealed similarities in findings on female distinctive symptoms compared with those that were not gender specific. These symptoms and their gender association are presented in Table 2 .
| Higher Prevalence in Women | Equal Prevalence by Gender |
|---|---|
| Nonrestorative sleep, fatigue Morning headache Insomnia Mood changes, irritability (features of depression) Sleep fragmentation; frequent awakenings |
Snoring Daytime sleepiness |
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