Sleep apnoea appears to worsen during the colder months of the year, according to a new study from Brazil.
Dr Jerome Dempsey, who studies breathing problems at the University of Wisconsin and was not involved in the new study, said it makes sense that airway infections and weather would have an effect on sleep apnoea. But the changes in sleep apnoea across seasons are small, Dr Dempsey added, and the study does not prove that winter weather in itself makes sleep apnoea worse.
Seasonal changes in weight and allergies can affect sleep apnoea, and the Brazilian researchers, led by Cristiane Maria Cassol at Universidade Federal do Rio Grande do Sul, wanted to see if weather changes might also have any impact on the disorder.
They used data from patients who came in for testing at a sleep clinic on how many times their sleep was disturbed by breaks in breathing. The study included one night of sleep for more than 7 500 patients over a 10-year period. The researchers then compared the severity of the patients' apnoea to the weather conditions at the time, including humidity, temperature, and air pollution.
Change of breathing patterns
Patients who came in during the colder months had more nighttime breaks in breathing than those who sought treatment during the warmer months. For instance, during the winter, patients stopped breathing an average of 18 times per hour, compared to 15 times an hour during the summer.
Similarly, the sleep clinic was more likely to see the most severe cases - people who stopped breathing more than 30 times an hour - in the colder months. About 34% of patients who came in during cold weather had severe apnoea, while 28% of patients during warm weather had severe apnoea.
Worse cases of apnoea
The team found that high atmospheric pressure and humidity and high levels of carbon monoxide were tied to worse cases of apnoea. The researchers write in their report, published 14 June in Chest, that more severe apnea in the winter "can be due to several circumstances, including winter-related upper-airway problems that intensify the severity of (sleep apnoea) symptoms."
Another possibility is that wood burning to heat homes during the winter can cause irritation in the airways and aggravate sleep apnoea. "There are so many things that affect sleep apnoea, including the decision of when to come visit" a sleep clinic, Dr Dempsey told Reuters Health. And of course the biggest risk factor is obesity, he added.
(Reuters Health, Kerry Grens, July 2012)
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