Where You Live Determines Your Ideal Amount of Sleep: 'No Universal Perfect Sleep Time'

We learn from an early age: an adult should sleep eight hours a night. But this advice turns out not to apply to everyone. New international research shows that your ideal amount of sleep strongly depends on the culture in which you live.

Scientists from Canada analyzed sleep data from nearly 5,000 people across twenty different countries. What did they find? The average sleep time varies greatly by country. Japanese sleep just over six hours a night on average, while the French get close to eight. The Dutch were in between with about 7.5 hours.

Yet, people in countries with shorter nights were not less healthy than those who slept longer. In fact, those who slept according to their cultural norm generally scored better on health metrics.

"There is no universally perfect sleep time," says researcher Steven Heine from the University of British Columbia. "What works for you is tied to what is normal in your culture." So while eight hours might be ideal in the Netherlands, it could be considered too much in Japan.

The researchers observed that people who slept close to their 'cultural sleep time' felt physically and mentally better than those who deviated significantly from it.

According to lead author Christine Ou, a nurse and researcher, the study suggests we need to rethink sleep advice. "Health recommendations that account for cultural differences are likely more effective."

In short: there is no magic number of hours for everyone. How well you sleep depends not only on your rhythm but also on where you live and what is considered 'normal' in your environment.