There is also a physiological effect of heat itself on our breathing. “Heat can also destabilize breathing control, increase fluid retention and promote dehydration, which can cause the upper respiratory tract to collapse and increase the likelihood of sleep apnea,” says Lucia Pinilla, another Flinders University researcher studying the topic.
At the same time, sleep apnea is expected to become an increasing problem for city dwellers due to the chronic effects of air pollution on breathing at night, and the condition is only expected to worsen. Last year, researchers from Hong Kong conducted the study where they found that both short-term and long-term exposure to PM2.5 particles – small airborne particles less than 2.5 micrometers wide that are produced from sources such as vehicle exhaust, factory emissions and wildfires and can penetrate deep into the lungs and bloodstream – increased the likelihood of sleep apnea.
Others have shown that the same applies to nitrogen dioxidea reddish-brown gas released into the air from exhaust pipes, power plants and other industrial facilities during exposure to pollutants also worsens symptoms for people suffering from sleep apnea.
“Obstructive sleep apnea occurs when the upper airway becomes unstable and collapses during sleep,” says Martino Pengo, an associate professor at the University of Milano-Bicocca who studies the topic. “Air pollution can increase this instability by irritating the throat tissues, making the airways narrow and more susceptible to collapse when muscle tone naturally decreases at night. Nitrogen dioxide is a strong respiratory irritant and can cause local inflammation that can disrupt sleep and destabilize breathing.”
Such studies, while disturbing, also point to possible ways to reduce the risk. Martha Billings, professor of medicine in the division of pulmonary, critical care and sleep medicine at the University of Washington, recommends using indoor air filtration devices if online air quality databases indicate your city is performing particularly poorly. “I would recommend this solution, especially if the air quality index is greater than 200, which can happen in the event of forest fires or other air stagnation,” she says.
Similarly, with rising temperatures, losing weight may be a way to reduce the risk of sleep apnea. Research has shown how overweight or obese people are more likely to have more severe episodes of sleep apnea in warm weather, with more habitual stopping and starting of breathing at night. Pinilla says it has to do with how accumulating fat tissue changes the body’s internal temperature regulation. “People with more fat mass tend to retain more heat and dissipate it less effectively, making it more difficult to maintain a comfortable body temperature at night,” he says. “On hot nights, this can lead to lighter and more fragmented sleep.”
Men, who are already more susceptible to sleep apnea because they are more prone to fat accumulation around the neck and have longer and more collapsing upper airways, are particularly at risk, as are those with pre-existing mental health problems or sleep disorders.
The Flinders team hopes to eventually be able to develop personalized heat advice and warning systems for people who are at higher risk of sleep apnea during heatwaves, as well as straightforward solutions that everyone can apply. They hope to get funding to conduct experiments in which people are given cooling mattress toppers or follow specific behavioral tips, such as staying well hydrated before going to bed, to see if this can actively prevent apnea in warmer weather.
“Ultimately, our goal is to develop practical, evidence-based recommendations that can be applied during heatwaves, especially for vulnerable groups and people at higher risk,” Pinilla says.