What country you live in determines how many hours of sleep you need per night to stay healthy, according to a new study from British Columbia researchers.
Of the 20 countries included in the study, people in Japan reported sleeping the least, averaging just over six hours per night, but were no worse off than their sleepier counterparts in France, who reported sleeping almost eight hours per night. In Canada, people tend to sleep around 7.5 hours per night.
How much sleep you need per night appears to be set by cultural norms, said Christine Ou, assistant professor in the school of nursing at the University of Victoria and the study’s lead author.
Ou’s research was published earlier this month in Proceedings of the National Academy of Sciences. It compared the sleep habits of 20 countries during the fall equinox, when most countries around the world have a 12-hour day and a 12-hour night.
“There’s no magic number like the eight hours we’re often told to aim for, because what is optimal will vary one country to another,” Ou told The Tyee.
That being said, most people around the world still don’t get enough sleep, she added. A good night’s sleep should leave you feeling rested and refreshed.
If you feel like you’re about to fall back asleep all morning you’re not getting enough, Ou said.
Not getting enough sleep can impact our health in a lot of ways.
Sleep reduces levels of stress hormones such as cortisol and helps flush beta-amyloid protein fragments out of our system, which are linked to Alzheimer’s disease, Ou said.
In the long term, not getting enough sleep can reduce a person’s life expectancy and increase their risk of heart disease, diabetes and obesity, according to the study.
Which is why it’s surprising the study found that countries with shorter sleep durations didn’t have higher rates of the negative health impacts associated with not getting enough sleep.
There’s over an hour-and-a-half difference between how much sleep people in Japan and France get in a night, which is a striking gap, said Steven Heine, a professor of social psychology at the University of British Columbia and co-author of the study.
The gap “shows we learn, to a degree, from our culture what is a good night’s sleep,” Heine said.
“We also found people who slept closer to their country’s norms tended to be healthier. So local cultural norms contribute to a healthy night’s sleep,” he added.
This study isn’t the first one to find that following cultural norms can improve a person’s health.
People who share the same religion or political views as those around them have been shown to have greater health and well-being, Heine said.
For people who don’t share the same religion or politics as the dominant culture they live in, this can mean seeking out other members of your minority group and working to foster bonds and build community, Ou said.
Why studying sleep is difficult
Dr. Kristin Fraser, a clinical professor of respirology and sleep medicine at the University of Calgary, said the field of sleep research is very complex.
Fraser was not involved in the research but said the study “reinforces what we know: sleep is very important to health and we need further research into these variable factors that include issues of biology, individual genetics, culture and social norms.”
Heine said this is a small study and that he and Ou are planning more research to better understand how we learn sleep-related cultural norms and how people in countries with such different sleep durations can all be getting a healthy night’s sleep.
While the study’s sample size of 20 countries is a good sample size, each country’s data pool looked at only around 250 people, Heine said.
He hopes future studies could work with data collected from wearable devices that measure sleep and activity, ideally including several thousand people for each country they compare.
This might help answer further questions, such as how we learn cultural norms around sleep when sleep tends to be a very private part of our lives.
Heine said sleep could be influenced by societal structures, like how early or late offices are open or when buses start and stop running. Maybe when we air prime-time TV plays a part, or people pay attention and learn from those around us when they talk about sleep, he said.
But more research is needed before he can say for certain.
Migrating or immigrating to a different country might also eventually influence a person’s sleeping habits.
In 2021, Ou and Heine worked on a study that compared sleep levels among Asian Canadian students, European Canadian students and Japanese students. The study found that Japanese university students got a lot less sleep than Asian Canadian and European Canadian students, who reported similar levels. Though Japanese students slept less, they reported better overall health. This suggests “people do acculturate to the local cultural environment,” Heine said.
Ou and Heine said they’re hoping their most recent study helps sleep scientists start to think about culture when trying to determine what a sleep duration could mean. More research is needed, however, they cautioned, before they can offer guidance to health professionals or the general public.
