How much sleep you get may depend on where you live, while the time at which you got to bed is more important than when you get up, according to a new study.

In Japan and Singapore, where people tend to go to bed later and wake up earlier, the average is around 7.5 hours. By comparison, the Dutch clock up eight hours and 12 minutes.

The findings come from a study published in Science Advances that compiled user-submitted data from an app designed to help people get over jetlag. The results look at the top 20 countries where the most app users lived.

Researchers from the University of Michigan found that a country’s average bedtime – not the time it wakes up – has the biggest impact on sleep duration.

Sleep duration, wake time and bed time in surveyed countries.
Image: A global quantification of “normal” sleep schedules using smartphone data by Olivia J. Walch, Amy Cochran and Daniel B. Forger.

The report suggests that lifestyle factors are behind a worldwide shortage of sleep.

Professor Daniel Forger, a researcher on the study, said in an interview with the BBC: “Society is pushing us to stay up late, our [body] clocks are trying to get us up earlier and in the middle the amount of sleep is being sacrificed.”

A lack of sleep has been linked to a range of health problems, from heart disease to diabetes, as well as poor performance in the workplace.

So who gets the most and least sleep?

Women sleep on average 30 minutes more than men each night. And middle-aged get the least sleep of all.

People who spend time outside in natural daylight are more likely to go to bed earlier and sleep for longer than those who spend most of their day in artificial light.

Time of sunrise and sunset and wake time and bedtime of participants.
Image: A global quantification of “normal” sleep schedules using smartphone data by Olivia J. Walch, Amy Cochran and Daniel B. Forger.

The study followed previous research that found that sunrise, sunset, and light exposure affects sleep timings. However, sunset seems to have the smallest impact, with the report showing that while solar cues do influence sleep patterns, they are easily ignored.

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