• Posted December 10, 2025

Rising Temperatures Disturbing Americans' Slumber, Study Says

Climate change is costing people some shut-eye, and a new study says it’s only going to get worse.

Higher daytime or nighttime temperatures slightly lower the amount of sleep a person gets, researchers reported in the December issue of the journal Environment International.

By 2099, people could be losing up to 24 hours of sleep each year due to rising heat, researchers projected.

“This work is an important step toward understanding how sleep is affected by environmental stressors like heat, which can increase the risk of disease and even death,” said lead researcher Jiawen Liao, a postdoctoral research associate in population and public health sciences at the Keck School of Medicine of USC.

“If we can help people sleep better, we may be able to reduce illness and save lives,” Liao said in a news release.

Hot weather can disturb sleep in several ways, researchers said in background notes. Heat prevents the body from cooling down, can trigger a stress response and reduces the time a person spends in deep sleep and REM sleep.

In turn, poor sleep increases the risk of many different health problems, including heart disease, breathing issues and mental health disorders, researchers said.

“We already know that when there are extreme heat events, more people die from cardiovascular disease and pulmonary disease,” Liao said. “What will this mean for population health as global temperatures continue to rise?”

For the new study, researchers analyzed sleep data collected for more than 14,000 adults, amounting to more than 12 million nights of sleep. The team compared people’s sleep against weather data for their area to see how temperature affects sleep.

Results showed that an 18-degree Fahrenheit difference in daytime temperature was associated with about 2.2 minutes of lost sleep, while the same increase at night was linked to more than 2.6 lost minutes of sleep.

“This may seem like a small amount, but when it adds up across millions of people, the total impact is enormous,” Liao said.

As one might expect, sleep loss is highest during the hot summer days from June to September, researchers said.

There also are geographic differences, with folks on the West Coast losing nearly three times as much sleep as people in other regions.

All told, U.S. adults could lose between 9 and 24 hours of sleep each year by 2099, depending on where they live, researchers projected.

Rising temperatures also were associated with more disrupted sleep throughout the night, and more time spent awake in bed, researchers said.

Researchers next plan to investigate whether indoor cooling, green roofs or better sleep hygiene can counter the effects of heat and help people get a good night’s sleep. They also plan to see whether improving sleep can reduce heat-related health problems.

More information

The Sleep Foundation has more on getting better sleep during hot weather.

SOURCE: Keck School of Medicine of USC, news release, Dec. 5, 2025