New research suggests that climate change may impact yet another valuable resource: our sleep.
In a study published in One Earth last month, researchers found that by 2099, higher temperatures may erode 50 to 58 hours of sleep per person every year, with each person subject to two weeks of temperature-attributed shortened sleep annually. Researchers estimated that by the beginning of the 21st century, temperatures had already caused the loss of 44 hours of sleep because of suboptimal nighttime temperatures, with 11 nights of short sleep per person.
“For most of us, sleep is a very familiar part of our daily routine; we spend nearly a third of our lives asleep,” Kelton Minor, the lead author of the study and a researcher at the University of Copenhagen, tells the Guardian’s Damian Carrington. “In this study, we provide the first planetary-scale evidence that warmer than average temperatures erode human sleep.”
Using sleep-tracking wristbands and a smartphone app, researchers collected sleep data from over 47,000 adults in 68 countries. They then mapped that data on to local daily meteorological data. They found that sleep loss and the risk of insufficient sleep increased steeply when temperatures rose above 50 degrees Fahrenheit (10 degrees Celsius). On warm nights—above 86 degrees Fahrenheit (30 degrees Celsius)—people slept an average of about 14 minutes less.
“Many of us already do not get enough sleep, and the contribution of sleep issues relevant to global warming could have real consequences for our health and well-being,” said Alex Agostini, a lecturer in the department of justice and society at the University of South Australia who was not involved in the research, to CNN’s Megan Marples in an email.
The researchers also found that like other impacts of climate change, the effects of climate-induced sleep loss will not be distributed evenly. Those living in lower income countries, the elderly and women will be most affected. Elderly people in particular tend to lose the ability to adjust to nighttime temperature increases and in general have shortened sleep durations. The effect of every one-degree-Celsius change on sleep is more than twice as harsh on the elderly than middle-aged or young adults, the study reports.
“Our results demonstrate that temperature-driven sleep loss likely has and may continue to exacerbate global environmental inequalities,” the authors write.
Surprisingly, people’s bodies didn’t seem to adjust to these warmer temperatures, even if they lived in warmer climates year-round or if they experienced a summer of hotter nights, per National Geographic.
“Humans are remarkably adaptive,” Minor tells National Geographic’s Alejandra Borunda. “But there are real physical limits to adaptation that we need to be mindful of.”
“It might actually be the tip of the iceberg, because it’s very likely our estimates are conservative,” Minor tells the Guardian. Those that wear sleep-tracking watches are more likely to have access to other technologies that can help keep them cool on hot nights.
“Lower-income people are underrepresented in the data and we’re very transparent about that,” Minor tells the Guardian, adding that further research is needed in warmer areas, including parts of Africa, Central America and the Middle East.
Susan Clayton, who studies the implications of climate change for psychological well-being at the College of Wooster, tells New Scientist that the paper’s methodology is sound.
“The implications are clear: higher temperatures associated with climate change are already reducing the amount of sleep people get and are projected to do so even more,” she tells the publication. “Since we know that lack of sleep can negatively impact mood, behavior, health and cognitive functioning, this is concerning.”