Being a man or woman also plays a role in the development of Obstructive sleep apnea (OSA). This relates to differences in airway size, fat distribution and hormone levels. In general, men are more likely to develop OSA especially when younger. But the risk for women increases after menopause. Women have smaller airways related to smaller soft tissues and airway caliber. Women also have smaller neck circumference, on average, and lower prevalence of central obesity, both linked to the risk of OSA. Additionally, women deposit fat in different parts of the body than men do; Men tend to carry their weight in the upper body, contributing to narrowing of the airway, while women tend to gain weight in the lower parts of the body.

Some differences in the severity and extent of symptoms have also been noted between genders. When comparing the impact of weight on sleep apnea, population studies have shown women weigh more for a given level of severity. For example, the average weight for an apnea-hypopnea index (AHI, the average number of times during sleep that breathing pauses or stops per hour, where higher numbers = more severe apnea) of 10 , might be 190 pounds in men and 200 pounds in women. Data from the Wisconsin Sleep Cohort Study, a large population based study, looking at AHI and weight in males versus females confirmed this outcome. This could be, as mentioned above, due to the fact that women tend to distribute weight differently than men. Therefore, greater total weight in women would be required to have similar amounts of fat deposition around the neck to men. It might also be secondary to other differences such as hormone differences.

Women of child bearing age have much higher hormone levels of estrogen and progesterone than men. These differences in female hormones might explain some of the decrease in incidence of OSA in women. Estrogen and progesterone levels drop after menopause, just as the risk of developing sleep apnea increases in women. However, studies on post-menopausal women, who have received hormone replacement therapy have shown variable results on their development of OSA. The exact relationship between hormones and OSA is unclear. It appears that hormone levels play a role in the decreased incidence of OSA in some women. However, the potential benefits of using hormonal therapy, at least for the decreasing risk of OSA is not proven at this time.

Sleep apnea may mimic other conditions in women

Recognizing the symptoms of sleep apnea in women is more difficult as women present to physicians later, with less typical complaints that may mimic other conditions. In addition to developing apnea later in life than their male counterparts, women are less frequently observed by others as having nighttime events of pauses to breathing which often leads individuals to seek medical attention. Instead, they may experience a lack of sleep at night that they may not even tell their doctors about. They may also complain of restless legs, nightmares, palpitations, and hallucinations. Some medical conditions that are related to sleep apnea may be more common in females such as a mood disorder or thyroid dysfunction. On the other hand, women are less likely to use substances that worsen apnea or disrupt sleep such as alcohol and caffeine.

Milder forms of OSA in females may mimic pain syndromes or psychiatric disturbances. A diagnosis of OSA is usually made if there is an apnea-hypopnea index (AHI, the average number of times during sleep that breathing pauses or stops per hour, where higher numbers = more severe apnea) of at least 5 on a sleep study. When symptoms from apnea occur with lower numbers it is usually referred to as upper airway resistance syndrome (UARS). Men with UARS often present with typical symptoms of sleep apnea such as daytime sleepiness and snoring. However, women often present with atypical symptoms, such as insomnia, fibromyalgia type symptoms such as muscle pain, or morning headaches, making the diagnosis more difficult in women. Women may also be complain of psychological disturbances such as depression, anxiety, fatigue and social withdrawal resulting from sleep apnea. Prior to menopause, complaints of changes in menstrual cycle, such as missed or very painful periods can also be seen.