Women sleep half an hour longer than men, phone app data shows

David Shultz — Fri, 06 May 2016 18:00:35 +0000

Time for a cat nap

Elliott Erwitt/Magnum

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.

Late nights in Singapore

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:

Find out more about the science of sleep in our topic guide

Exoskeleton reveals lengths we go to save energy when walking

David Shultz — Fri, 11 Sep 2015 09:26:00 +0000

Walk this way, no that way (Image: Greg Ehlers) Ever waited for a bus rather than take the short walk to work? Headed for the escalator instead of the stairs? Humans clearly harbour a deep love of lethargy – and now we know how far people will go to expend less energy. We will change our walking style on the fly when our normal gait becomes even a little more difficult. The finding could have implications for the rehabilitation offered to people with spinal injuries. and her colleagues at Simon Fraser University in Burnaby, British Columbia, Canada, strapped volunteers into a lightweight robotic exoskeleton and put them on a treadmill. Initially, the team let the volunteers find their preferred walking rhythm – which turned out to be 1.8 steps per second, on average. Then the researchers switched on the exoskeleton, programming it to make it more difficult for the volunteers to walk at their preferred pace by preventing the knee from bending – and leg swinging – as freely. The exoskeleton didn’t interfere with the human guinea pigs’ ability to walk faster or slower than they preferred. Within minutes the volunteers had found a walking style that the exoskeleton would allow without offering resistance. Remarkably, though, they did so despite the fact that the exoskeleton only ever offered minimal resistance. By using breathing masks to analyse the volunteers’ metabolic activity, Selinger’s team found that subjects would shift to an awkward new gait even if the energy saving was only 5 per cent. “People are able to adapt and fine-tune in order to move in the most energetically optimal way,” says Selinger. “People will change really fundamental characteristics of their gait.” Put another way, millions of years of evolution, and the experience we each glean from the millions of steps we have taken, can seemingly be overwritten in moments for the sake of making tiny energy savings. That’s not to say it wasn’t evolution that dictated our predilection for laziness in the first place. “If you look way back in time, we would have been trying to conserve as much energy as we could,” says Selinger. Before food became so accessible – and escalators so abundant – perhaps the ideal strategy for survival was energy-efficient endurance rather than speed. The finding might be bad news if you’re trying to burn as many calories as possible on the treadmill at the gym – your brain might subconsciously find energy-saving shortcuts – but Selinger points out that plenty of other physical activity is enhanced by our energetic efficiency. Running a marathon, for instance, might be made easier by our ability to make these tiny energy savings. , a biomedical engineer at the University of Southern California, thinks the findings may shed light on how people recovering from strokes or spinal injuries may learn to walk again. Particularly significant is the fact that the volunteers had to explore different walking styles before they would shift their gait. “If you want a patient to find a new energetically optimal behaviour you may need to force exploration,” he says. And perhaps people recovering from injury need to know that trying to walk as they did before isn’t necessarily the best approach. “It might be that we need to rethink how we rehab someone,” says Selinger. Journal Reference:

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Women sleep half an hour longer than men, phone app data shows

Late nights in Singapore

Exoskeleton reveals lengths we go to save energy when walking

David Shultz, Author at ��è��Ƶ