Snoring & Sleep Apnoea in Women
Why is snoring and sleep apnoea not easily recognised in women?
Snoring and sleep apnoea are generally considered to be conditions predominantly affecting men. The basis for this assumption is made purely on early epidemiological studies and clinical research conducted on male patients. Studies from the early 1970s and 1980s suggested that the male:female ratio for sleep apnoea was around 60:1. However, more recent research has recognised that snoring and sleep apnoea in women is not as rare as was once thought. More recent studies on general populations have reported male:female prevalence ratios for sleep apnoea are around 2:1.
But despite these findings, the greater prevalence of snoring and sleep apnoea in men still tends to promote an unintentional 'selection bias' for referral. Some studies have found that men are twice as likely to be referred for a sleep study than women. Many GPs rely on self reported snoring and sleep apnoea, and because men are more likely to seek help about snoring from their GP, they are more likely to receive an early referral for a sleep study. Nearly half of women snorers do not report their symptoms to their GP, often due to embarrassment or shame, but they do tend to be heavier users of healthcare resources prior to a diagnosis being confirmed.
Undiagnosed or misdiagnosed?
The few population studies that have included women, show undiagnosed sleep apnoea is far more prevalent in women than men. One study found that sleep apnoea was undiagnosed in more than 90% of women with moderate to severe sleep apnoea. One hypothesis that has been put forward is that because women often present with symptoms that differ from the current clinical indications for the evaluation of sleep apnoea, the condition may be missed or misdiagnosed. For example, in one study, nearly half of the female patients did not report apnoea events, choking or restless sleep to their GP but all the males did.
Snoring is a costly business
A study comparing health care costs among patients with snoring and sleep apnoea, found both sexes incur nearly double the healthcare costs of normal patients, but women incur significantly more costs than men. Both sexes have considerably more consultations with specialists and women have nearly 50% more visits compared to men. Similar figures have been found for drug costs, with women being prescribed antidepressant drugs three times more frequently than men. The results of the study concluded that snoring women tend to have more minor illnesses and atypical symptoms while men with the same severity of snoring have more chronic and fatal diseases.
The symptoms of snoring and sleep apnoea have an adverse effect on neurological and psychological function resulting in poor work performance, difficulty in concentrating, memory impairment, headache, nausea, impotence and decreased libido. These symptoms have the same effect on both men and women.
Same disease, different symptoms
Typical symptoms of sleep apnoea, snoring, apnoeas, choking and restless sleep, are similar in both men and women. However, snoring women tend to present with additional symptoms that may be misinterpreted to represent other conditions. Atypical symptoms such as daytime fatigue, headaches, insomnia, tension, depression and the use of sedatives are more frequent in women than men and may divert GPs and clinicians to diagnose and treat for other conditions. For example, because women are more likely to report insomnia and depression they are more likely to be treated for these symptoms rather than the underlying cause of their sleep apnoea.
Women don't fit the stereotype
Nearly half of all middle aged men snore, but women tend to snore later in life with an increased prevalence after menopause at around 60-64 years of age. Additionally, snoring sound in women is less intense therefore snoring may not be such an issue for younger women.
Obesity and fat distribution
Obesity seems to be the dominant factor for the occurrence of sleep apnoea in women when matched with males for age and degree of sleep disturbance. One study reported that women had a higher BMI (body mass index) than men at each level of RDI (respiratory disturbance index). There is evidence that obesity is greater in premenopausal women compared to postmenopausal women with sleep apnoea. It has also been reported that premenopausal women have more severe apnoea compared to postmenopausal women with the same BMI. It was reported in the same study that women who snore but without apnoea were not obese. However, morbid obesity occurs twice as often in women compared to men and since obesity is the main risk factor for the development of sleep apnoea, one might predict that women should have sleep apnoea more frequently than men. But evidence supports the opposite. Perhaps the argument for obesity as a risk factor for sleep apnoea in women is not obesity per se, but rather a matter of fat distribution.
There is a relationship in overall neck size and airway obstruction, and men have a higher proportion of fat around the neck area compared to the rest of the body, than do women. Men tend to have a greater volume of fat in the soft palate and the upper part of the tongue whereas women tend to have greater fat deposition in the lower part of the airway. Women also tend to have less upper airway anatomical abnormalities and require greater fat infiltration before they have a reduction in airway space.
Craniofacial anatomy could be an important factor in the prevalence of snoring and sleep apnoea. Both men and women who snore or have sleep apnoea have differences in craniofacial anatomy compared to the normal population.
It is known that men have significantly larger airways and pharynx than women. But despite this fact, their pharynx is more prone to collapse. Although the airways of women are narrower they are stiffer and less likely to collapse. Men also have less muscle tone in their upper airways making them more vulnerable to snoring and sleep apnoea.
Female hormones may have a protective effect on the upper airway dilator muscles as they are believed to protect the airway from obstructing during sleep. However, hormone replacement therapy (HRT) in postmenopausal women has yielded conflicting results. Some studies found modest improvements in snoring and sleep apnoea with oestrogen alone, whilst others found better improvements with both oestrogen and progesterone. Some studies however, found no improvements at all.
Testosterone on the other hand, has been found to increase upper airway collapsibility and the consequent risk of developing snoring and sleep apnoea. An interesting study on males with gonadal dysfunction found that when they were treated with testosterone replacement their snoring and sleep apnoea doubled in severity during the treatment. Similarly, it was reported that women with polycystic ovary syndrome (characterised by an excess of male hormones) had a 4-fold increase in the risk of snoring and sleep apnoea. This may explain in part why there is a male predominance in snoring and sleep apnoea.
Excessive daytime sleepiness, fatigue, decreased libido, depressed mood, headache, impaired concentration and obesity are all symptoms associated with snoring and sleep apnoea. But they are also symptoms of hypothyroidism. Hypothyroidism in snoring women is statistically higher than it is in men. This may be another reason why snoring and sleep apnoea in women are confused or misdiagnosed. In patients with hypothyroidism, sleep disordered breathing appears to be common, yet in patients with snoring or sleep apnoea, hypothyroidism is very uncommon. The reasons why this should be are still unclear. There does appear to be a positive link between obesity and hypothyroidism. In one study with obese individuals, their snoring and sleep apnoea reduced significantly following hormone therapy, as did their BMI. Thyroxin therapy was also given to snorers who were not obese, and similar results were obtained with a reduction in their snoring and excessive daytime sleepiness. This connection between hypothyroidism and snoring and sleep apnoea is interesting and is worthy of further research.
There is an increasing interest in the association between snoring, sleep apnoea and diabetes mellitus. Diabetes is often associated with snoring and sleep apnoea, predominantly in overweight males. However, one study of women aged 25-79 years found diabetes in snoring women independent of age, obesity or smoking status. Snoring women were twice as likely to suffer diabetes than non- snoring women.
Both diabetes and snoring and sleep apnoea are influenced by sexual hormones. Snoring and diabetes often increase during pregnancy, after the menopause and in women with Polycystic Ovary syndrome. The sleep deprivation and cyclic decreases in oxygen levels that occur as a result of snoring and sleep apnoea tend to increase insulin levels. It has been suggested that this may be the link between snoring and diabetes as one study reported that insulin sensitivity improved following treatment for snoring and sleep apnoea.
In summary, two factors seem to be prominent; hormones and airway resistance. The influence of hormones may be the most important determinant in the differences between men and women, but airway mechanics and collapsibility seem the most likely mechanism that would explain the predominance of snoring and sleep apnoea in men.
We should be aware of the additional atypical symptoms in women; of fatigue, headaches, insomnia and depression, and of the importance of further investigation to prevent under detection and under treatment of snoring and sleep apnoea.