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Fully half of the 400 women given overnight sleep tests in a new Swedish study turned out to have mild-to-severe sleep apnoea.
In the random population sample of adult women who answered a questionnaire and were monitored while sleeping, half experienced at least five apnoea-hypopnoea episodes per hour (i.e., periods when they stopped breathing for longer than 10 seconds), the minimum definition of sleep apnoea.
Among women with hypertension or obesity the proportion was even higher, reaching 80% to 84%. Many of the women in the study had mild cases of sleep apnoea.
"How important is the mild sleep apnoea, we don't know," said lead author Dr Karl Franklin of Umea University. But Dr Terry Young of the School of Medicine and Public Health at the University of Wisconsin said of mild sleep apnoea, "We see that it doesn't go away and it gets worse."
Sleep apnoea complications
One recent study found that women who have sleep apnoea are more likely to develop memory problems and dementia.
Dr Franklin and his colleagues selected 400 women between the ages of 20 and 70 from a larger population sample of 10 000, and asked them to sleep overnight at home, wearing sensors that measured heart rate, eye and leg movements, blood oxygen levels, air flow and brain waves.
The study, which was funded by the Swedish Heart Lung Foundation, found that apnoea became more common in the older age groups.
Among women aged 20-44, one quarter had sleep apnoea, compared to 56% of women aged 45-54 and 75% of women aged 55-70.
Dr Young said these numbers are higher than her own estimate, but that's likely because she uses a more strict definition of sleep apnoea than Dr Franklin's group.
Dr Franklin also said his equipment, being newer, is more sensitive in detecting interruptions in breathing.
No more excluding women
Severe sleep apnoea, involves more than 30 apnoea-hypopnoea episodes per hour, was far less common, occurring in 4.6% of women 45-54 and 14% of women 55-70.
Rates of severe sleep apnoea were 14% in women of all ages with hypertension and 19% in women who were obese.
Dr Franklin said that if physicians are looking for sleep apnoea among women, examining those who are obese, over 55 or have hypertension is a good place to start.
Dr Young said sleep apnoea is often thought of as a condition of men, but identifying women with it is especially beneficial, because her research has shown that women are more likely to comply with treatment.
"The prejudice of excluding women (as potentially having sleep apnoea) has been rampant for a long time. It's gotten better, however, and the (public health) gain in identifying women with sleep apnoea is great," she said.
The study was reported in the European Respiratory Journal.
(Reuters Health, September 2012)
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