Most research looking at the impact of climate change on human life has focused on how extreme weather events affect economic and societal health outcomes on a broad scale. Yet climate change may also have a strong influence on fundamental daily human activities — including a host of behavioral, psychological, and physiological outcomes that are essential to wellbeing. In a study published May 20th in the journal One Earth, investigators report that increasing ambient temperatures negatively impact human sleep around the globe.
The team says their findings suggest that by the year 2099, suboptimal temperatures may erode 50 to 58 hours of sleep per person per year. In addition, they found that the temperature effect on sleep loss is substantially larger for residents from lower income countries as well as in older adults and females.
“Our results indicate that sleep — an essential restorative process integral for human health and productivity — may be degraded by warmer temperatures,” says first author Kelton Minor of the University of Copenhagen. “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.”
It’s long been known that hot days increase deaths and hospitalizations and worsen human performance, yet the biological and behavioral mechanisms underlying these impacts have not been well understood. Recent self-reported data from the United States have suggested that subjective sleep quality decreases during periods of hot weather, but how temperature fluctuations may impact changes in objective sleep outcomes in people living across a variety of global climates has remained unclear.
“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.”
To conduct this research, the investigators used anonymized global sleep data collected from accelerometer-based sleep-tracking wristbands. The data included 7 million nightly sleep records from more than 47,000 adults across 68 countries spanning all continents except for Antarctica. Measures from the type of wristbands used in this study had previously been shown to align with independent measures of wakefulness and sleep.
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