Rising temperatures driven by climate change are negatively impacting human sleep patterns around the globe, a new study has found.
If temperatures continue to surge, the effects could slash between 50 and 58 hours of sleep per person each year by the end of the century, according to the study, published on Friday in One Earth. The impacts will be substantially larger for residents of lower-income countries, as well as older adults and women, the authors determined.
“Our results indicate that sleep — an essential restorative process integral for human health and productivity — may be degraded by warmer temperatures,” first author Kelton Minor, of the University of Copenhagen, said in a statement.
“In order to make informed climate policy decisions moving forward, we need to better account for the full spectrum of plausible future climate impacts extending from today’s societal greenhouse gas emissions choices,” Minor added.
To conduct their study, the researchers used anonymized global data collected from sleep-tracking wristbands.
The data included 7 million nightly sleep records from more than 47,000 adults across 68 countries — on all continents aside from Antarctica, according to the study. Measures from these types of wristbands, the authors explained, had previously been shown to align with other independent measures of wakefulness and sleep.
On very warm nights — those with temperatures above 30 degrees Celsius, or 86 degrees Fahrenheit — sleep amounts dropped an average of more than 14 minutes, the researchers observed. They also found that the likelihood of getting less than seven hours of sleep rises alongside temperature increases.
“Our bodies are highly adapted to maintain a stable core body temperature, something that our lives depend on,” Minor said.
“Yet every night they do something remarkable without most of us consciously knowing,” he added, explaining that human bodies shed heat into the environment by dilating blood vessels and increasing blood flow to the hands and feet.
But in order for sleeping humans to accomplish this heat transfer, the surrounding environment needs to be cooler than their bodies are, according to Minor.
While previous studies in sleep labs have determined that both humans and animals sleep worse when the room temperature is too hot or cold, such research was limited by the fact that people tend to modify the temperature of their sleeping environment to make themselves more comfortable, the authors noted.
In this study, the investigators found that under normal living routines, people tend to be better at adapting to cooler outside conditions than warmer ones.
The authors also observed that residents of developing countries seem to struggle more with rising temperatures. While a lack of sufficient air conditioning may play a role, the researchers said that they could not formulate a definitive conclusion on this factor, as they did not have access to relevant data on air conditioning.
Future research on the impact of rising temperatures on sleep, they noted, should focus on how sleep loss is unequal globally — with a particular look at the world’s most vulnerable populations who reside in the hottest environments.