Did you sleep well? The answer may depend on your age, location and gender. A survey of 5000 sleepers from across the world has revealed that women get the most sleep, particularly those under the age of 25.
Daniel Forger at the University of Michigan in Ann Arbor and his team were able to get their huge dataset thanks to Entrain, a smartphone app that people use to track their sleep. With their consent, Forger’s team accessed users’ data on their wake time, bed time, time zone and how much light they were exposed to during the day.
Analysing this information, they found that middle-aged men sleep the least, while women under the age of 25 sleep the most. As a whole, women appear to sleep on average for 30 minutes longer than men, thanks to going to bed slightly earlier and waking up slightly later.
For an individual, the time they woke up had the strongest link to how much sleep they got, suggesting that having a job that starts early every day can mean that you get less sleep than someone who starts work at a later hour.
Aussies hit the sack earlier
There were also differences between countries. People in Singapore, for example, sleep for an average of 7.5 hours a night, while Australians get 8.1 hours. Late bedtimes seem to be to blame – people in Singapore tended to stay up until after 11.45 pm each night, while people in Australia were likely to hit the hay closer to 10.45 pm.
The team found that, in general, national wake-up times were linked more to daylight hours than bedtimes. This could be because bedtimes are more affected by social factors.
The app data also revealed that, as people got older, they tended to go to sleep and wake up earlier, suggesting that the window for when a person can sleep narrows with age. “As one gets older it becomes harder to sleep at certain times and therefore people schedule their sleep at those times,” says Forger.
If you’re already going to bed early but would like to sleep better, here’s a tip: go outside. Forger’s team found that people who are exposed to outdoor light sleep more than those who are largely exposed to indoor light – although this might be because outdoor occupations are more tiring.
So much of what we know about sleep only comes from lab studies, says Stanford University behaviour scientist Jamie Zeitzer, who was excited about the citizen science aspect of the study. “It’s giving us a very different view of how sleep looks in the real world.”
Journal reference: Science Advances, DOI: 10.1126/sciadv.1501705