I can’t sleep when it’s hot out. I just lie there, wide awake and growing increasingly irritated by any bird, bug, car, or human that makes even the slightest noise. When morning finally rolls around, I’m grouchy, sweaty, and covered in a bizzarro maze of pillow lines from my wadded-up sheets. The pillow lines are sweaty, too.
Well, science has some bad news for me: climate change could mean more nights of crappy sleep in the future. Increasing temperatures make it harder for people’s bodies to cool down — a prerequisite for a good night’s sleep. And more unusually warm nights in the years to come could make for a nation of grumpy, unwell people — particularly in the northern and western parts of the US, according to a study published today in the journal Science Advances.
Scientists have long known that temperature is key to getting a good night’s rest. As we start getting sleepy, the blood vessels in our skin expand and our hands and feet get warmer. That helps the body lose heat to the environment, dropping its core temperature — a signal that it’s time to go to sleep, and stay asleep. But if it’s too warm out, the body can’t cool itself down as well, which can mess with sleep quality. That made a group of scientists at Harvard and the University of California, San Diego want to know: what’s going to happen when temperatures climb up?
About 50 to 70 million people in the US already have problems sleeping (and not just because sometimes it’s hot out). If you get too little sleep, your brain doesn’t work as well, your muscles don’t repair themselves, your immune system bails, and you up your risk for heart disease. The authors of the study sum it up nicely: “Human well-being suffers without adequate rest.” (The humans around me also suffer when I’m not adequately rested.)
To figure out how climate change could affect sleep, the scientists first analyzed health-related surveys conducted by the Centers for Disease Control and Prevention from 2002 to 2011. The question they were particularly interested in was, “During the past 30 days, for about how many days have you felt you did not get enough rest or sleep?” By linking each answer to the date someone took the survey and the city they lived in, the researchers could determine the number of unusually warm nights in those previous 30 days.
The researchers discovered that warmer-than-average temperatures increase the number of bad nights that people report — particularly in the summer. A temperature hike of 1.8 degrees Fahrenheit (1 degree Celsius) upped the number of poor night's sleep by three nights per 100 individuals per month. So across the US, that would mean 9 million bad nights of sleep each month, or 110 million nights of overly warm tossing and turning each year.
Lower-income people without air conditioners and older people whose bodies can’t regulate temperature as well are hit especially hard, the study finds. In fact, the effects of warmer nights on sleep are 10 times greater for people who are both lower income, and over age 65.
This just tells us about temperatures in the recent past, though. What about the future? Using data from NASA, the scientists projected that unusually warm nights would mean another six nights of poor sleep per 100 people by the year 2050, and an additional 14 by 2099. That’s two extra weeks of grumpy mornings and sweaty pillow lines. Based on their data, the researchers predict that these nighttime temperatures will veer farthest from average in western and northern regions of the country — which means these places will be hit especially hard.
Given how important sleep is for human well-being, that means even more Americans may suffer from chronic health issues in the future. Thanks, climate change.