Montrealers who sleep poorly at night when it’s warmer than usual aren’t alone.
According to study published in the environmental science journal One Earth, warmer temperatures have a direct impact on the average person’s ability to fall asleep and stay asleep.
“People were sleeping less, and the likelihood that nights of sleep got shorter increased as temperatures rose,” said Kelton Minor, lead author of the study and PhD student at the University of Copenhagen’s Social Data Center.
The study involved 47,000 people in 68 countries using the special bracelets and combined their sleep data with each participant’s local weather and climate data.
The study comes after climate data show that – even with conservative estimates of greenhouse gas emissions – the number of nights per year where temperatures do not fall below 20°C is expected to more than quadruple over the next 60 years in some parts of Canada.
Montreal, for example, has historically averaged about eight such nights per year, according to Climate Atlas of Canada. But over the next 30 years, that number could rise to 19–22 nights at these temperatures, and then to 28–45 in the next three decades.
The project also predicts that Montreal’s heatwaves, defined as consecutive days when temperatures rise above 30°C, will last an average of three days in 2005 to eight days by 2080.
Minor’s research also suggests that the ideal sleep temperature for the average person may be around or below 5°C, so sleep can be severely affected during the summer months for those without air conditioning, and electricity bills are likely to rise for those with he is.
According to the study, the average person now loses approximately 40 hours of sleep per year due to excessive nighttime temperatures, with older people, women and people living in poorer countries suffering disproportionately.
The number of hours of sleep lost is projected to increase to 50-58 hours, depending on society’s ability to adapt and mitigate change.
“If we come up with new technologies that help lower nighttime temperatures and protect sleep, perhaps their impact will decrease,” Minor said. “On the other hand, if the world’s population continues to age, the average person may become more vulnerable to the effects of rising temperatures.”
“Anything that upsets our balance will also interfere with our sleep,” said Roger Godbout, professor at the University of Montreal and director of the sleep clinic at the Riviere de Prairie Hospital.
Godbout added that elevated temperatures are no exception as they directly affect people’s ability to fall asleep and how often they wake up.
Studies have shown that some animals are able to adapt to sleep at lower temperatures for several weeks, but there is no evidence that they or humans can adapt to sleep at higher temperatures, he said.