Here's why napping is good for you, according to science.

What do staff at NASA, Google and Samsung have in common?

They can all go for a nap at work in a specially designed sleep pod.

Engineers, programmers and astronauts can lie down in the pod for 20 minutes at a time. With the outside world shut out by a large visor, the pod plays soothing sleep music before gently waking its occupant up with natural light patterns.

The company behind the pods, New York-based MetroNaps, also supplies law firms, management consultancies, and airlines. Any business, in fact, that is “interested in attracting and retaining good-quality employees”, MetroNaps chief executive Christopher Lindholst told the Financial Times in a recent interview.

But the trend for naps at work is far from being just the latest way of pampering over-privileged workers.

Instead, it is a movement backed up by scientific evidence.

Deprivation dangers

One of the best arguments for napping is the damage that can be caused by sleep deprivation.

A recent study in the journal Nature Medicine points out that sleep deprivation has been linked to a whole range of health problems, including obesity, diabetes, stroke, heart attack, and even death.

Death may be caused by long-term sleep deprivation leading to various health problems.

But it can also be caused in an instant by a driver falling asleep at the wheel or an over-tired surgeon making the wrong incision.

The study, by neuroscientists and psychiatrists at American, French, and Israeli universities, examined how the brain behaves when it is deprived of sleep.

It found that losing one night’s sleep stops our brain working properly. Neurons fire more slowly than usual, meaning our brain takes longer to translate visual input into conscious thought.

When a pedestrian steps out in front of your car, these extra seconds can mean the difference between life and death.

Sleep revolution

If lack of sleep can be so deadly, how much sleep is enough to ensure our brains function properly?

Current guidelines recommend between seven and nine hours every night for adults.

After collapsing from chronic fatigue in 2007, Huffington Post founder Arianna Huffington has become a sleep evangelist.

When launching her book The Sleep Revolution last year, she said: “We need to dispel the myth that we can function perfectly on four or five hours.”

As well as supporting a good night’s sleep, Huffington is also a fan of napping. She has introduced nap rooms to the Huffington Post offices, claiming “having a nap in the middle of the afternoon is actually a performance-enhancing tool”.

Her claims are backed up by a wealth of research showing the benefits of topping up on sleep during the day.

Napping benefits

Probably the most famous example of an afternoon nap is the Spanish siesta.

Researchers at the Spanish Society of Primary Care Physicians (SEMERGEN) in 2012 claimed that going without sleep is worse than going without food for maintaining the same level of activity in the afternoon.

The researchers recommend an afternoon nap – preferably after eating – of no more than 30 minutes.

This is backed up by a study of Chinese people aged 65 and older, which found post-lunch napping improved their cognitive abilities.

A NASA study of astronauts’ sleep patterns found that the main cognitive function improved by napping was “working memory”. This is the ability to multitask – focusing attention on one task while holding other tasks in memory.

Working memory is a fundamental ability for performing complex work like piloting a spaceship.

In addition to improving cognitive abilities, other studies have shown napping reduces the risk of heart disease.

University of California psychology professor Dr Sara Mednick, author of Take a Nap! Change your Life, goes even further in listing the benefits of napping.

She claims it “increases alertness, boosts creativity, reduces stress, improves perception, stamina, motor skills, and accuracy, enhances your sex life, helps you make better decisions, keeps you looking younger, aids in weight loss, reduces the risk of heart attack, elevates your mood, and strengthens memory”.

Don’t overdo it

Despite napping’s many benefits, you can have too much of a good thing.

The authors of the NASA study on astronauts’ sleep patterns warn that napping for too long can send you into a deeper sleep, which can leave you feeling drowsy after waking up – a phenomenon it calls “sleep inertia”.

Equally, the researchers behind the Spanish study on siestas suggest that too much sleep in the day is harmful to your quality of sleep at night.

So what is the ideal nap time?

While the participants of the Chinese study napped for more than an hour, most research suggests that the best naps end before you enter deep sleep.

As this occurs at around half an hour into sleep, anything less than 30 minutes is considered optimal.

This is the reason that air traffic controllers in the US are told to take 26 minute naps, and that the sleep pods occupying the offices of Google and Samsung wake you up after 20 minutes.