A new study finds climate change’s impact on ambient temperatures could impact sleep patterns around the world.
On the heels of the heatwave that saw India and Pakistan reach average daily temperatures of 92°F and highs of more than 120°F last month, research published last week finds rising global temperatures could lead to a global sleep deficit. The new research is published in the journal One Earth.
According to the research, by the 22nd century, suboptimal global temperatures as a result of climate change could mean a decrease of nearly two percent per night. This number would be even higher in lower-income regions as well as for older adults and women.
“Our results indicate that sleep—an essential restorative process integral for human health and productivity—may be degraded by warmer temperatures,” the study’s lead 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.”
While the effects of high temperatures are already known to increase the risks of death and hospitalizations, the study is the first of its kind to look at the role planetary temperatures play in sleep health—especially over time.
“In this study, we provide the first planetary-scale evidence that warmer-than-average temperatures erode human sleep,” Minor says. “We show that this erosion occurs primarily by delaying when people fall asleep and by advancing when they wake up during hot weather.”
The researchers looked at more than seven million nights of sleep data from more than 47,000 individuals in 68 countries. A pattern emerged suggesting very warm nights—warmer than 86°F, sleep declined on average by more than 14 minutes per night, increasing the likelihood of getting a minimum of seven hours of sleep per night.
“Across seasons, demographics, and different climate contexts, warmer outside temperatures consistently erode sleep, with the amount of sleep loss progressively increasing as temperatures become hotter,” Minor says.
The findings suggest that people are better at adapting to colder outside temperatures than hotter conditions. But in order for our bodies to be able to distribute and transfer heat, the surrounding environment needs to be cooler than we are.
“Our bodies are highly adapted to maintain a stable core body temperature, something that our lives depend on,” Minor says. “Yet every night they do something remarkable without most of us consciously knowing—they shed heat from our core into the surrounding environment by dilating our blood vessels and increasing blood flow to our hands and feet.”
While air conditioning could help to mitigate the issue, it’s not a viable solution for much of the developing world or more than 1.2 billion people currently. It’s also currently reliant on fossil fuel-powered energy grids.
Energy production is the leading contributor to human-caused climate change. The recent IPCC report urged for drastic reductions in emissions by 2025 to keep global temperatures from surpassing 1.5°C over pre-industrial levels per Paris Agreement targets.
Experts around the world agree that consistent sleep is paramount to optimal health. While sleep requirements differ from person to person at any given time, most research points to between six to eight hours per night for healthy adults.
Quality and consistent sleep may also help in the fight against climate change itself. A 2018 study found that those who were better rested showed more empathy to people in distress than those who hadn’t been as rested.