Getting less than seven hours of sleep a night on a regular basis, the bare minimum for adults, has also been linked to heart problems, obesity and type 2 diabetes, among others. “People try to get naps during the week and catch up on the weekends, but the health and cognitive benefits of sleeping properly during the week never fully recuperate,” says Miller.
And with climate change, many people around the world are now experiencing hot, sleepless nights. Compared to the early 21st century, night-time temperatures are hotter today, meaning that every person worldwide loses an average of 44 hours of sleep per year compared to 2010. That also means, on average, adults experience 11 extra nights each year where they get less than the seven hours of sleep they need.
As air temperatures continue to rise, people could be missing out on even more. A recent study linked the sleep-tracking bracelets of more than 47,000 people in 68 countries to local meteorological data and predicted that individuals could lose 50 hours of sleep per year by the end of the century compared to 2010. Six extra lost hours spread over the year between now and then might not seem like much, but this would result in about 13 extra short nights of sleep, which is hardly desirable.
The study’s researchers also looked at whose sleep was most disturbed. “We hypothesized and expected that people already living in warm climates would be better adapted to nighttime temperature rises,” says Kelton Minor, a PhD student at the University of Copenhagen’s Center for Social Data Science and lead author of the study. “What we found was the complete opposite.” According to the analysis, which is based on data from 2015 to 2017, a 1-degree rise at night appears to hit those in the world’s warmest climates more than twice as hard as those in the coldest regions.
They also found that the sleep loss per degree of warming appeared to be greater in women, the elderly and people in low-income countries. Although the study design did not allow any causal conclusions as to why this is so, some conjectures can be made based on existing research: Women’s bodies usually cool down earlier in the evening to prepare for sleep than men’s, so it Women gets hotter, more bothersome temperatures when their sleep wave hits. Women also have higher levels of subcutaneous fat, which can slow the nighttime cooling process, making body temperature control more difficult during heat waves. And as we age, the body releases less melatonin, which could explain why older people have even more trouble regulating their body temperature when it’s too hot.
Fans and air conditioners can help remove heat from the body or cool a bedroom, but in low-income countries, most people don’t have access to such devices. Apart from that, sleep researcher Blume has no panacea for getting enough sleep on hot nights. “Anything that helps lower body temperature would make sense from a sleep perspective,” she says. Even something as simple as sleeping with a thin blanket or no blanket at all, or a cooling hand and foot bath before bed is useful — as long as the water isn’t too cold, otherwise your body will start to compensate and produce heat, she says.
Removing electronic devices (which give off heat) from your room, keeping curtains, blinds, and windows closed during the day, and staying hydrated can also help. “You just have to try things. The main thing is to relax,” says Blume. But when you’re lying there muggy and sweaty, that’s easier said than done.