Rising Temperatures Are Taking a Toll on Sleep Health

There is also the physiological effect of heat itself on our breathing. “Heat can also destabilize respiratory control, increase fluid retention and promote dehydration, which can make the upper airways more pliable and increase the risk of sleep apnea,” says Lucia Pinilla, another Flinders University researcher studying the topic.

At the same time, sleep apnea is already expected to become a growing problem for people living in cities, due to the chronic impact of air pollution on nighttime breathing, a problem that will only get worse. Last year, researchers in Hong Kong conducted a study in which they found that short- and long-term exposure to PM2.5 particles – tiny airborne particles less than 2.5 micrometers wide, generated by sources such as vehicle exhaust, factory emissions and wildfires and which can penetrate deep into the lungs and bloodstream – made sleep apnea more likely.

Others have shown that the same is true for nitrogen dioxide, a reddish-brown gas released into the air from exhaust fumes, power plants and other industrial facilities, while exposure to pollution also worsens the symptoms of people with 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 Milan-Bicocca who studies the subject. “Air pollutants can increase this instability by irritating throat tissues, making the airways narrower and more likely to collapse when muscle tone naturally decreases at night. Nitrogen dioxide is a potent airway irritant and can promote local inflammation that can fragment sleep and destabilize breathing.”

While worrying, this research also points to possible ways to mitigate risks. Martha Billings, professor of medicine in the division of pulmonary, critical care and sleep medicine at the University of Washington, advises using indoor air filtration devices if online air quality databases show your city ranks particularly poorly. “I would especially recommend it if the air quality index is above 200, as can happen with wildfires or other stagnant air,” she says.

Likewise, with temperatures rising, losing weight could be a way to mitigate your risk of sleep apnea. Research has found that people who are overweight or obese are more likely to experience more severe episodes of sleep apnea in hot weather, with their breathing stopping and starting more often during the night. Pinilla says this is related to how the accumulation of body fat changes the body’s internal temperature regulation. “People with higher body fat tend to retain more heat and dissipate it less efficiently, making it more difficult to maintain a comfortable core temperature at night,” she says. “On hot nights, this can lead to lighter, more fragmented sleep.”

Men, who are more vulnerable to sleep apnea anyway because they are more prone to accumulating neck fat and have longer, more pliable upper airways, are particularly at risk, as are those with pre-existing mental health or sleep disorders.

The Flinders team hope to eventually develop personalized advice and heat alert systems for those at greater risk of suffering from sleep apnea during heatwaves, as well as simple solutions that everyone can turn to. They hope to get funding so they can conduct experiments in which people are given cooling mattress pads or follow specific behavioral advice, such as making sure they are well hydrated at bedtime, to see if this can actively prevent apnea episodes in hot weather.

“Ultimately, our goal is to develop practical, evidence-based recommendations that can be applied during heat waves, especially for vulnerable groups and those most at risk,” says Pinilla.