Sex differences and sleep apnoea

Although obstructive sleep apnoea is a highly prevalent disorder with major public health ramifications for both men and women, very little is known about sex differences in the pathogenesis of this disorder. Initial studies1-3 indicated that sleep apnoea was much more common in men than in women. It was originally thought that the male to female ratio for obstructive sleep apnoea was approximately 8:1.1-3 However, more recent and rigorous epidemiological studies2 4 have shown that the male to female ratio for sleep apnoea is in the range of 2:1. Young and colleagues4 reported that the prevalence of obstructive sleep apnoea associated with excessive daytime sleepiness in the 30–60 year old population is 4% in men and 2% in women. Gislason and coworkers2 estimated that the lower limit of the prevalence of sleep apnoea in middle aged Icelandic women was 2.5%. These studies indicate that sleep apnoea is common in women. Moreover, studies have shown that the clinical presentation of sleep apnoea is similar in men and women, although the prevalence is higher in men.5 One reason for the higher prevalence in men may be that women are less likely to report symptoms associated with sleep apnoea.6 However, several studies7-10 have demonstrated sex differences in the structure and physiological behaviour of the upper airway. Such data imply that sex differences in the prevalence of sleep apnoea are not solely related to the under-reporting of symptoms but rather are related to pathological differences in the presentation of this condition in men and women.

What are the possible mechanisms underlying the differences in the pathogenesis of obstructive sleep apnoea in women and men? Two important determinants of upper airway luminal calibre are the activity of the upper airway dilator muscles, which tend to increase airway …