ANYONE who’s tried to sleep on a hot summer night knows how hard it is to nod off when the mercury is rising. So it’s no surprise that global warming is likely to cost people more and more shut-eye as temperatures around the world rise. By the end of this century, individuals could be subjected to at least two weeks of short sleep each year due to high temperatures driven by global warming, a new study projects. The findings were published May 20 in the journal One Earth. It’s even worse for certain vulnerable groups, particularly older folks, said lead author Kelton Minor, who did the research as a doctoral student in planetary social and behavioral data science at the University of Copenhagen in Denmark. “The estimated sleep loss per degree of warming was twice as large among the elderly compared to younger or middle-aged adults, three times larger for residents living in lower-income versus high-income countries, and significantly larger for females than males,” Minor said. “Importantly, we found some evidence that the temperature-sensitivity of sleep in late adulthood may become elevated between the ages of 60 and 70, with the magnitude of estimated sleep loss per degree of warming increasing further for those older than 70,” he said. Minor said these projections are based on data from a first-of-its-kind “planet-scale natural experiment,” in which more than 47,600 people from 68 countries wore sleep-tracking wristbands from September 2015 through October 2017. Minor and his colleagues then compared the 7.4 million sleep records they’d gathered against local weather and climate data, to see how heat affected each participant’s sleep. “We found that nights that were randomly warmer than average eroded human sleep duration within individuals globally,” Minor said. “We estimated that people slept less and the probability of having a short night of sleep increased as nights became hotter.” Data show that on very warm nights — 86 degrees Fahrenheit or higher — sleep declined an average of just over 14 minutes, and the likelihood of getting fewer than seven hours of shut-eye increased as temperatures rise. Specifically, people tended to nod off later and wake up earlier during hot weather, researchers said. They also found that people already living in warmer climates experience greater sleep erosion as temperatures rise, and that people don’t adapt well to temperature-caused sleep loss in the short-term, Minor said. “Adults didn’t make up for lost sleep over subsequent nights, didn’t compensate for nighttime sleep loss with daytime rest and did not appear to acclimatize to more common warmer temperatures over the summer period,” he said. Running these numbers through two climate change scenarios, researchers found that people will be losing sleep as the planet warms, no matter what. (SD-Agencies) | 