“I WAS very conscious of the fact that I was dying,” says Nick Moloney. At the time he was trapped underneath the hull of his yacht as it hurtled through the Atlantic. His arm was broken, and his lungs were full of water. “I gave up the struggle,” he says.
Just in time the boat slowed down and righted itself, scooping Moloney up with it. He lay on the deck, gasping for air.
That was back in 1999. Australian Moloney blames himself for the disaster, putting it down to lack of sleep. Solo racers must cope with sleep deprivation for days or sometimes weeks on end, often adopting an unusual sleep pattern where they snatch their rest in 20-minute catnaps in between scanning the horizon for threats such as icebergs. But in this race, Moloney had felt compelled to make do with almost no sleep in a bid to recover time.
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By the fifth day without sleep, he was beginning to drift in and out of consciousness. “I made stupid mistakes, and I basically forgot how to sail,” Moloney admits. The mast was damaged and at one point, the yacht was going backwards. When a massive wave struck, Moloney was in an unsafe position and was thrown into the water.
“By the fifth day without sleep he was drifting in and out of consciousness”
After his narrow escape, Moloney was forced to pull out of the race. The experience left him determined to learn how to cope with the extreme sleep deprivation of solo yacht racing. For the past few years he has worked with scientists in a bid to hone his sleep patterns to get maximum recuperation from the least down time. It’s a strategy he feels was vindicated in 2002 when he returned to the same transatlantic course for the two-week solo Route du Rhum race. He finished 370 kilometres ahead of his nearest competitor, beating the record previously held by his friend and sometime crewmate Ellen MacArthur.
Now, however, Moloney faces a much stiffer challenge. This week, along with 20 other competitors, he is due to begin the toughest solo yacht race of them all, the round-the-world Vendée Globe, in which MacArthur famously came second in 2001. The 42,000-km non-stop race, which encircles Antarctica, takes more than three months to complete.
Few of us experience the extreme sleep deprivation of solo sailors. But perhaps many of us could benefit from learning the art – and science – of napping. Evidence is starting to emerge about the timing and length of naps that gives the most benefit. The research is attracting interest from the airline industry, where alert staff are crucial for safety. Shift workers, motorway drivers, jet-lagged travellers, emergency workers and even new parents could also benefit from learning to tailor naps to their specific requirements. “It’s a question of helping people to find their own ideal in terms of managing sleep,” says Claudio Stampi, head of the Chronobiology Research Institute in Newton, Massachusetts, who has coached Moloney in the science of napping.
To understand how naps work, a lightning tour is needed of the different stages of sleep through which an adult brain cycles on a typical night (see Graphic). The different brain waves of each phase are revealed by electrodes placed on the scalp, to give what is known as an electroencephalogram (EEG) recording. The night starts with stage 1, the drowsy transition phase, progressing within minutes to the first proper sleep, stage 2. Within 15 to 25 minutes, the brain descends into deeper sleep, called stages 3 and 4 or “slow-wave” sleep. By now, the person’s heart rate has slowed and breathing is steady. Slow-wave sleep lasts for 30 to 50 minutes before the brain re-ascends through stage 2, to a 5 to 10-minute burst of rapid eye movement (REM) sleep, in which dreaming occurs and the brain seems almost awake. Then the cycle repeats.
Perhaps surprisingly, there is still no consensus on the various functions of the different stages of sleep (żěè¶ĚĘÓƵ, 28 June 2003, p 28). But many scientists think slow-wave sleep is the most important phase. It is not distributed evenly through the night, but crammed into the first half, suggesting it is a priority. “If you are restricted to 3 hours’ sleep a night, you probably get all the slow-wave sleep you need,” says Jim Horne, head of the Sleep Research Centre at Loughborough University in the UK. And the more sleep-deprived people are, the more rapidly they sink into stages 3 and 4.
In contrast to most people’s habit of having one long sleep during the night and staying awake through the day, many solo yacht racers adopt “polyphasic” sleeping. Here the long sleep is replaced with 10 to 15 naps lasting 20 or 30 minutes, dispersed through the day.
Over the past 20 years, Stampi has studied more than 100 solo sailors, and finds that most survive on polyphasic sleep totalling an average of about five hours a day, perhaps for weeks at a time.
It would be impractical to record EEGs in a race of course, but Stampi has studied volunteers in the lab restricted to 3 hours’ sleep in 24 for a few days. In these circumstances, polyphasic sleep produces as much total slow-wave sleep as monophasic, he says. And he suggests that for people who are sleep-deprived, polyphasic sleep may actually be superior to one long sleep because it “recharges the batteries” so frequently. “It’s easier than we expected to adapt to,” says Stampi. “Some people actually seem to like it.”
For most people, however, polyphasic sleep is neither necessary nor desirable. Most of us can fit in a reasonably long stretch of shut-eye. But if our sleep is too short or too interrupted, it can be useful to top it up with brief daytime naps that boost immediate performance.
So how long should they be? That depends how long you have to recover afterwards. The way you feel when you wake up varies dramatically depending on what stage of sleep you were in at the time. People woken while in slow-wave sleep feel groggy, a phenomenon known as sleep inertia, and this may take up to half an hour to shake off. People usually wake naturally in a light phase of sleep, and become alert more quickly.
A short nap of just 10 to 15 minutes works well for a quick recharge, says Horne. It provides a top-up of stage 2 sleep, enough to improve performance in tasks such as driving. A shift worker finishing at 2 pm after 8 hours of work, for example, might feel sleepy getting into the car for the drive home. Ten to 15 minutes of stages 1 and 2 sleep before setting off would improve reaction times behind the wheel for a couple more hours, and possibly save lives. Crucially, a nap as short as this does not usually allow slow-wave sleep to kick in, unless someone is truly exhausted. Without slow-wave sleep, there should be no sleep inertia to overcome. A longer nap of say 50 minutes can improve performance for longer, but also requires a lengthier recovery while the grogginess wears off. So, if you’re a shift worker operating heavy machinery during the night, or a car driver taking a break, only take the longer nap if you’ve got at least 20 minutes to wake up properly before taking the controls.
Sleepy pilots
The timing of naps can also affect their usefulness. Humans have their own daily clocks that include naturally sleepy times and naturally wakeful times, resulting in part from hormone and temperature changes. Most people find it comparatively easy to catnap at around 2 pm, when there is a natural dip in alertness. But around 8 am or 6 pm are for most people alert and wakeful times. The early evening wakeful period can be a problem for shift workers who try to go to bed early in anticipation of an early morning start.
Perhaps most important for any of us who fly long haul is the alertness of the crew. The UK contract research company Qinetiq has been investigating the best napping strategies for pilots on behalf of the British Civil Aviation Authority. Based on this the CAA issued advice last year on what to do if a member of a two-pilot crew feels unexpectedly sleepy (). It recommends a nap of about 30 minutes, set within an hour-long rest period. This allows 10 minutes to settle to sleep and 20 minutes or so to wake up afterwards. Qinetiq has also developed a computer program that predicts pilots’ tiredness, based on factors such as early starts and jet lag, which is now being used to help to plan the sleep schedules of the four pilots needed on ultra-long-haul flights.
The CAA report also highlights a phenomenon many may recognise. If a sleeper is aware that they may be disturbed, by a call to work or a crying baby, say, they sleep more lightly. This was first shown back in 1988, when Swedish scientists persuaded ships’ engineers on a rota of overnight on-call duty to hook up to EEG machines while they slept. When on call, the engineers experienced less slow-wave sleep and less REM sleep. Think how often you turn over and check the alarm on the night before an early flight, says Barbara Stone at Qinetiq. “It’s as if the brain has taken itself up to a higher level,” she says. But exactly how this is accomplished is still unclear.
Perhaps the most unglamorous section of the sleep-deprived population, more neglected than airline pilots, are new parents. These shocked, dazed individuals may lose as many as 350 hours of sleep in the first year of their infants’ lives. Horne’s group at Loughborough is studying another sleep-deprived group, the carers of people with Alzheimer’s disease, who have chronically unpredictable sleep patterns. Unsurprisingly, his advice for new parents and carers is just to grab sleep whenever possible. Don’t worry about whether it’s a 15-minute nap or two hours, he says: just take it.
Horne’s research, which has not yet been published, suggests that women are better at coping without sleep than men; they can keep going for longer and perform better on various cognitive tests. The women tended to slow down in the tests, while maintaining their accuracy, he says. The men tended to keep to their normal speed, at the expense of accuracy.
Could women have evolved to deal better with sleep deprivation because they tend to provide more childcare? Perhaps, but the skill may be learnable. Horne points out that in his tests, the women tended to pace themselves better, conserving their energy for the long term. “The men rush around doing press-ups because they think they’ll keep themselves awake that way. What they forget is that the exercise makes them feel sleepy.”
Moloney knows that if he is to complete the Vendée Globe, he will have to make every minute of sleep count. Qinetiq scientists have been helping him fine-tune his sleep patterns over the past few months, using a wrist-worn activity monitor that provides a read-out of time spent asleep and awake. He has been training himself to get by on minimal rest, and practising falling asleep quickly. He can now drop off in the time it takes for a set of traffic lights to go through its cycle, he says. His secret is to swiftly eradicate thoughts of the boat and fill his mind with irrelevant thoughts instead.
Will he cope with the three months ahead? Moloney knows that the risks of the race are significant, but he feels ready for them. Then he looks forward to coming home and getting on with his life – and catching up on his sleep.
- Follow Nick Moloney’s progress at