10 Jun Sex differences in OSA
Obstructive sleep apnoea (OSA) is a condition that affects both men and women, however it’s long been observed that men are at higher risk. The reason for this disparity is complex and not fully documented, with possible causes including anatomy of the upper airway, fat distribution, hormones, and arousal response. For instance, men typically have a longer and more collapsible upper airway, predisposing them to airway collapse during sleep. On the other hand, women exhibit unique anatomical features, such as a shorter oropharynx and differences in fat distribution, which may offer some protection against OSA. However, the precise interplay between these factors and their relative importance in modulating OSA risk remain subjects of ongoing research.
Obesity is strongly associated with OSA, with BMI correlating positively with the severity of the disease, particularly in men. Despite women having a higher prevalence of obesity, they are less frequently diagnosed with OSA, and one theory is differences in fat distribution. While weight gain leads to fat accumulation in the tongue, women tend to have lower Mallampati scores (relative size of the base of the tongue compared to the oropharyngeal opening), suggesting that fat plays a smaller role in their airways compared to men.
Various mechanisms have been proposed to determine how gender-specific hormones might influence the susceptibility of individuals to OSA. One theory suggests that these hormones play a role in shaping body fat distribution. Typically, men exhibit higher lean tissue mass and lower fat mass compared to women of the same age. However, postmenopausal women tend to have increased fat mass, particularly in the android (upper body and trunk) regions, contrasting with the gynoid (lower body) distribution seen in premenopausal women. The proportion of android fat tends to rise with age and time since menopause, with the latter being a significant predictor of body fat mass and trunk fat. Additionally, women, regardless of age and total fat body mass, may experience a preferential accumulation of visceral (abdominal) fat. These findings suggest that acquiring a “male/android” pattern of fat distribution, especially post menopause, may increase the risk of developing OSA.
Optimising OSA management requires a tailored approach that considers gender-specific factors. While CPAP therapy remains the gold standard of treatment, interventions targeting modifiable risk factors, such as obesity, and addressing hormonal influences through hormone replacement therapy (HRT) when appropriate, can enhance treatment outcomes.
Reference:
Lin CM, Davidson TM, Ancoli-Israel S. Gender differences in obstructive sleep apnea and treatment implications. Sleep Med Rev. 2008;12(6):481-496. doi:10.1016/j.smrv.2007.11.003