We all have cause to take climate change personally. Not only do higher temperatures lead to such mega-events as droughts, heat waves, wildfires, and floods, they also affect human health—exacerbating asthma, allergies, cardiovascular disease, the spread of water-borne pathogens, and more. Now, it appears that a warming world affects us in one other, potentially life-threatening way. That’s according to a new, yet-to-be-peer-reviewed paper presented May 18 at the 2025 gathering of the American Thoracic Society in San Francisco. Researchers found that as the heat increases, so too does the incidence and severity of obstructive sleep apnea (OSA), increasing the risk of hypertension, heart attack, stroke, and death.
“We were surprised at the magnitude of the association between ambient temperature and OSA severity,” said Bastien Lechat, the lead author of the paper and a senior research fellow at South Australia’s Flinders Health and Medicine Research Institute, in a statement that accompanied the recent presentation. “This study really highlights the societal burden associated with the increase in OSA prevalence due to rising temperatures.”
In order to conduct their work, Lechat and his team collected data from 125,295 users of an under-mattress apnea sensor, in 41 countries, gathering readings recorded from January 2020 to September 2023. The sensor consists of an inflatable mat positioned beneath the point of the mattress that is at chest level with the sleeper. Changes in the air pressure within the mat record bodily, respiratory, and even cardiac motion. “By analyzing these signals with proprietary machine learning … the device can estimate a range of metrics, including sleep duration, sleep stages, awakenings, and periods of breathing cessation,” Lechat said in an email to TIME. Those cessations in breathing are what constitutes apnea.
The researchers collected a median of 509 nights of readings from each individual, and then correlated the results with 24-hour ambient temperature models. The results were striking, showing a significant association between apnea and temperature in 29 of the countries studied, or well more than half. In those places, rising heat was associated with a 45% increase in the likelihood of an individual having at least one apnea episode on a given night. That does not come cheap. Crunching their numbers, the researchers estimated that across the sample group, the increase in apnea incidence resulted in a loss of more than 785,000 healthy life years—or years without disability or death—in 2023 alone. Loss of healthy life years has an economic cost too, with an estimated $32 billion reduction in workplace productivity in 2023.
The connection between rising temperatures and OSA is not new. Climate change brings with it more extreme heat, including while we sleep. Nighttime temperatures often bring a cool relief, but in many places around the world these drops in temperature aren’t falling as low as they once did. The researchers estimate that the health and economic hit from growing heat-related apnea has increased 50% to 100% since 2000. Going forward, a rise in average global temperature of 2°C over pre-industrial levels can be expected to lead to a 1.5- to 3-fold OSA increase by 2100. Already the world surpassed 1.5°C of warming in 2024.
“Our economic estimates in the paper suggest that increased OSA prevalence driven by higher ambient temperatures could lead to a multi-trillion-dollar global societal cost, along with poorer human health and well-being,” says Lechat.
For now, the mechanism linking temperature and the cessation of breathing is not clear. Lechat and his colleagues speculate that heat may lead to lighter sleep—which is the stage of sleep during which apnea tends to be more severe. Behavioral factors may be at play too: when temperatures are higher, individuals may be less likely to wear their continuous positive airway pressure (CPAP) masks, which are prescribed to reduce or prevent apnea.
Whatever the cause, we may all feel the effect. “Sleep is the third pillar of health, alongside nutrition and exercise,” says Lechat, “[It] is essential for both physical and mental well-being.”
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