Global sleeping patterns revealed by app data
The world's sleeping patterns have been revealed by scientists analysing data collected from an app.
It showed the Dutch have nearly an hour more in bed every night than people in Singapore or Japan.
The study, published in Science Advances, also found women routinely get more sleep than men, with middle-aged men getting the least of all.
The researchers say the findings could be used to deal with the "global sleep crisis".
The team at the University of Michigan released the Entrain app in 2014 to help people overcome jetlag.
But users could choose to share data on their sleeping habits with the research group.
The study found people in Japan and Singapore had an average of seven hours and 24 minutes sleep while the people in the Netherlands had eight hours and 12 minutes.
People in the UK averaged just under eight hours - a smidgen less than the French.
And it was a country's average bedtime that had the biggest impact on the time spent between the sheets.
The later a country stays up into the night, the less sleep it gets. But what time a country wakes up seems to have little effect on sleep duration.
Prof Daniel Forger, one of the researchers, said there was a conflict between our desire to stay up late and our bodies urging us to get up in the morning.
He told the BBC News website: "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; that's what we think is going on in global sleep crisis.
"If you look at countries that are really getting less sleep then I'd spend less time worrying about alarm clocks and more about what people are doing at night - are they having big dinners at 22:00 or expected to go back to the office?"
The study also showed women had about 30 minutes more per night in bed than men, particularly between the ages of 30 and 60.
And that people who spend the most time in natural sunlight tended to go to bed earlier.
A strong effect of age on sleep was also detected. A wide range of sleep and wake-up times was found in young people but "that really narrows in old age," said Prof Forger.
Dr Akhilesh Reddy, from the University of Cambridge, told the BBC: "I think it's interesting; there's been a trend for these studies using data from twitter and apps and finding interesting correlations across the world we've never been able to do by putting people in sleep lab.
"It highlights that although our body clocks are programming us to do certain things, we can't as we're ruled by social circumstances.
"We won't know the long-term consequences of this for many years."
Disrupted sleep in shift workers has been linked to a range of health problems, including type 2 diabetes.
Dr Reddy said the next wave of studies would gather data from activity and sleep monitors and "that's where the future of this is".
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