Japan’s sleep mystery: How sleeping less may still mean living longer

Japan’s average sleep lasts barely more than six hours, yet the country has the longest life expectancy among developed economies and one of the world’s lowest obesity rates. A study highlighted by RTS suggests the explanation may lie less in the number of hours people sleep than in how sleep fits into their culture.

Researchers Kristin Ou and Steven Heine analyzed sleep and health data from nearly 5,000 people in 20 countries, controlling for factors including diet and smoking. Their central question was whether the ideal amount of sleep is universal.

The results showed a broad range in average sleep, from 6 hours and 18 minutes in Japan to 7 hours and 52 minutes in France. The study concluded that there is no single magic number. People appeared healthier when their sleep habits matched the norms of the society around them, a pattern the researchers called “cultural fit.”

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Is the ideal amount of sleep universal?

Ou said, “Our basic physiological needs are shaped by interaction with culture.” The article says this alignment with social rhythms may reduce the practical and psychological stress caused by schedules that do not fit local expectations.

At the national level, countries where people sleep less did not show higher rates of heart disease or diabetes, nor shorter life expectancy. They had lower obesity rates than countries where people slept longer. The article points to diet, physical activity and social cohesion as potentially important factors.

It also describes Japanese habits surrounding sleep, including fish-rich diets, daily movement, hot baths before bed and sleeping on futons on tatami. Afternoon naps, known as inemuri, are culturally accepted and viewed as a sign of hard work. The source text ends while describing this practice.

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Our basic physiological needs are shaped by interaction with culture.