Electronics and artificial lighting are fundamentally changing our sleep patterns.
It’s no surprise that our bodies and minds take a toll when we don’t get enough sleep. Sleep quality can have a direct impact on our lives, but a new study reveals some concerning findings about the way society is changing our natural sleep habits.
The study, led by University of Michigan mathematicians, combined mathematical modeling, mobile apps, and big data to gauge the ways society and biology affect sleep schedules. They used a free smartphone app, called Entrain, that helps travelers avoid jet lag by adjusting to new time zones.
Entrain was released by the researchers a few years ago, and it recommends custom schedules of light and darkness. To fine-tune recommendations to each individual, users have to plug in information about their typical hours of sleep and light exposure. The quality of the app relies heavily on the accuracy of the inputted information, so the researchers say this motivated users to be particularly careful in reporting their sleep habits.
The researchers explain that our bodies are governed by an internal biological clock, our circadian rhythms, which are fluctuations in our bodily functions or behaviors that are tied to the planet’s 24-hour day.
“Sunrise and sunset fix the window of sunlight available to this clock,” the researchers write in the study, “whereas social factors, such as cultural norms or work obligations, modulate the amount of light reaching the clock through selective blocking of light during the day or the use of electric light at night.”
Our circadian rhythms are set by a “grain-of-rice-sized cluster of 20,000 neurons behind the eyes,” the press release explains, and they’re regulated by the amount of light our eyes take in. Now that we’re living in an increasingly electronic world, our eyes are taking in a lot more artificial light than previous humans were ever exposed to.
Naturally, this is affecting our sleep schedules.
"Across the board, it appears that society governs bedtime," Daniel Forger, of the U-M Medical School's Department of Computational Medicine and Bioinformatics, said in a press release.
"At the same time, we found a strong wake-time effect from users' biological clocks—not just their alarm clocks. These findings help to quantify the tug-of-war between solar and social timekeeping."
After analyzing the data collected from the Entrain app, the researchers found that the national averages of sleep duration varied between countries around the world. Residents of the Netherlands had the maximum sleep duration, with an average of 8 hours and 12 minutes each night, while people in Singapore and Japan had the minimum average duration of 7 hours and 24 minutes.
While the window between the two doesn’t seem too drastic, the researchers stress that every half hour of sleep makes a big difference when it comes to cognitive function and long-term health. In fact, the CDC says that sleep deprivation increases the risk of heart disease, obesity, diabetes, high blood pressure, stroke, and stress.
The researchers also found that middle-aged men tend to get the least sleep, and women tend to go to bed earlier and wake up later than men, which gives them about 30 more minutes of sleep on average. Also, those who spend some time in the sunlight each day tend to go to bed earlier and get more sleep than those who spend most of their time in indoor lighting.
Co-author Olivia Walch says that even getting six hours of sleep a night builds up a “sleep debt.”
"It doesn't take that many days of not getting enough sleep before you're functionally drunk," she said. "Researchers have figured out that being overly tired can have that effect."
“And what's terrifying at the same time is that people think they're performing tasks way better than they are,” she explained. “Your performance drops off but your perception of your performance doesn't."
Aside from the less-than-thrilling study findings, which appear in the journal Science Advances, the researchers say that the research demonstrates that mobile technology can be a cheap and reliable way to gather massive data sets.
"This is a cool triumph of citizen science," Forger said.
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