How many of us as children wouldn't think of sleeping for a hundred years with absolute horror? As far as fairytale fates go, Sleeping Beauty didn't do too badly (no Huntsman on the loose, for example). But in the eyes of a child there can be no worse fate than a seemingly limitless period of enforced inactivity. You could say it's a real … snooze. But for a busy, working adult, with no time to spare for a day off, let alone an early night? Hand me the spindle, Maleficent. I'll see you in a month or two.

For best brain performance, the one thing never up for negotiation is how much sleep we need.

Full. Stop.

Here's the thing. We spend roughly one-third of our life asleep, yet our understanding of why we sleep, and its relevance to our mood, cognition and wellbeing, is still very young. In a world that often views sleep as a bit of a nuisance, something that stands in the way of our doing other things, knowing why we need sleep is critically important to our high-performance thinking.

Respect the zeds

Doing with less sleep appears to be another of those little badges of honour that have crept into office culture. For chronic insomniacs who would do almost anything to get just five more minutes' sleep, this has to be the ultimate insult. Why? Because the implication is we're being more disciplined, and in some way superior, if we deliberately cut back on our sleep.

Political leaders such as Winston Churchill and Margaret Thatcher famously got by with only four hours' sleep every night. Good for them, but they are in a very tiny minority of people who can do this and still function normally. Though Winston was perhaps equally famous for his daily naps — more on those later.

Scrambled eggs and sleep cycles

How much sleep is needed to function well will depend on a number of factors, including what animal you are. Humans tend to sleep for anything from five to 11 hours, with the average being seven and three-quarters hours. A cat sleeps for over 12 hours yet a giraffe needs less than two hours. Dolphins are even niftier with their sleep, being able to effectively shut down one hemisphere of their brain at a time so they can stay constantly alert for predators.

Generally we need between seven and eight hours of uninterrupted sleep for maximum restorative and rejuvenating benefit. Each night we experience between four and six sleep cycles, each lasting approximately 90 minutes.

During these cycles we spend some time in what is called deep sleep and some time in what is called REM (rapid eye movement) sleep (see figure 3.1). Far from resting, the sleeping brain is highly active, reactivating those neurons that were stimulated during the day, sifting through all the information accumulated, evaluating what we consider is important, and then forming and consolidating our long-term memories.

Dreaming is associated mainly with REM sleep. Dreams, or ideas recalled from them, are often credited with inspiring creativity. Paul McCartney based the tune of ‘Yesterday’ on a dream (for those inclined to get strange things stuck in their heads, the original lyrics involved scambled eggs and lovely legs). Jack Nicklaus attributed an improvement to his golf swing to a dream. The idea for Dr Jekyll and Mr Hyde came to Robert Louis Stevenson in a dream, or would that have been a nightmare?

How do you know if you're getting enough (sleep)?

Your partner may be able to answer this better than you can! If you wake feeling cognitively refreshed, that's a good indication you have had sufficient sleep.

Waking just before your alarm goes off, or not needing an alarm at all, and feeling fresh as a daisy, means you have had enough sleep.

Taking out the trash

Being metabolically highly active, the brain accumulates a lot of waste that needs to be removed. This happens mainly during sleep (well, at least in mice brains!), when our neurons physically shrink to allow our glymphatics, special channels made out of glial cells, to flush out the waste. This process occurs 10 times faster while we sleep than it does in our waking hours.

One concern about sleep deprivation is that it denies the brain its required cleaning time, and may contribute to the acceleration of age-related cognitive decline and neurodegenerative conditions such as Alzheimer's and Parkinson's disease. Maiken Nedergaard likens the system to a fish tank. Keeping the tank clean with a filter is essential to keeping those fish alive.

The same goes for our neurons.

Too tired to sleep

One of the commonest complaints I hear about is a difficulty not so much in falling asleep but in staying asleep. Having an over-busy brain can lead to a disturbed sleep pattern with frequent awakenings. The result? We wake up feeling tired, we go to work tired, we come home tired and we are always craving sleep.

With over 400 different recognised sleep disorders to choose from, it's a wonder any of us ever get a good night's sleep.

A series of blows to the cognition

The impact of sleep deprivation on our cognition includes:

• a slower response speed
• increased variability of performance
• impaired levels of creativity, innovation and diversity of thought
• impairment of those brain functions more dependent on emotional input, including decision making
• mood disturbance, with higher levels of anxiety and depression
• reduced motivation.

It can take us up to six weeks to recover from one night's lost sleep. Reducing our sleep time to four or five hours a night over as little as one week reduces our cognitive capacity to the equivalent of a blood alcohol level of 0.01 per cent.

People talk about being ‘punch-drunk’; one of the literal definitions of this is being dazed and confused from lack of sleep.

Sleep matters to our thinking ability just as much as healthy nutrition and physical exercise. It is a necessity, not a luxury.

Worse still, being sleep deprived causes us to lose the ability to recognise that we are tired and cognitively impaired. This is why sleep-deprived drivers continue to drive: their tired brain hasn't told them they need to stop.

I'd die to go to sleep

Yes, lack of sleep can be deadly.

Fatal Familial Insomnia, while fortunately incredibly rare (known to affect only 40 families around the world), is a genetic prion disease. It manifests in middle age as an increasing inability to fall asleep that leads to death within a few months or several years.

Staying awake for longer has often been seen as a game. Teenagers are the group most likely to pull an all-nighter or stay up partying. Back in 1965, 17-year-old Randy Gardner set out to see if he could set the record for staying awake. He still retains that official record of 11 days and 24 minutes. Others have also attempted to climb the Mount Everest of sleep deprivation, with the National Sleep Research Project claiming an unofficial record of 18 days, 21 hours and 41 minutes.

This is definitely not something to try at home, with side-effects that include hallucinations, paranoia, blurred vision, slurred speech, impaired memory and concentration lapses.

Sleep deprivation is now recognised as a global public health issue. According to the World Association of Sleep Medicine (WASM), sleep problems affect around 45 per cent of the world's population. Thirty per cent of Americans claim they don't sleep well, with between 50 and 70 million people reported as having a sleep or wakefulness disorder:

• 44 per cent reported getting less than seven hours' sleep
• 29 per cent reported either falling asleep or feeling very sleepy while at work
• 12 per cent admitted to having been late for work because of sleep.

The economic burden of the associated presenteeism has been estimated by Kessler and others to be US$63.2 billion. Similar figures have been collected elsewhere, with the Sleep Health Foundation reporting 13 to 33 per cent of Australians reporting having difficulty either getting to sleep or staying asleep, and studies from Morphy and others revealing 37 per cent of adults in the UK suffer from insomnia.

Sleep cycle expert Charles Czeisler, when asked about the problem of sleeplessness in an interview with the Harvard Business Review, advised corporate leaders, ‘If you want to raise performance — both your own and your organization's — you need to pay attention to this fundamental biological issue’.

Swing shift

Working too many hours on top of insufficient sleep can lead to an increase in errors and accidents. Some of the world's most catastrophic accidents, including the Exxon Valdez oil spill off Alaska, the space shuttle Challenger disaster and the Chernobyl nuclear accident, have been linked to sleep deprivation.

When it comes to working excessively long hours, doctors have historically been among the worst culprits. When I worked as a medical intern in the UK in the eighties, it was expected that our work would be hard and challenging, and the hours long.

Very. Long.

For a junior doctor, working what was known as a 1:2 meant being on duty for 36 hours, having one night off and then starting the next 36-hour shift. And we were charged with taking care of others' health!

Once, while driving home in the early-morning rush hour, brain-befuddled after a busy night-shift in the emergency department, I completely ignored a set of traffic lights and drove straight across a busy intersection. I'm not sure who was more horrified — those in the other vehicles or me when I realised what I had done.

I was lucky that time, but how often are workers expected to travel or drive tired?

Sleepless in Seattle, Tokyo, London, Sydney …

Executives are frequently required to travel interstate or overseas for work. Dealing with changes of time zone, navigating around an unfamiliar city, perhaps driving on the other side of the road — all add to the cognitive load on a tired brain.

A company whose work culture accepts sleep deprivation as the norm is putting its employees and its own longevity on the line.

When flying long distances for work, choosing not to travel on red-eye flights and, whenever possible scheduling in an additional day for our body clock to adjust, helps keep our mind clear and our thinking coherent.

Once, sleeping your way to the top had a certain connotation. Today ensuring that all staff, especially those aspiring to climb the corporate ladder, get enough sleep makes very good business sense.

Some people choose to stay awake or work nights:

• for the relative peace and quiet it affords
• because it's part of their job description (emergency workers, FIFO personnel, call centre staff)
• out of simple economic necessity (single-parent families, say, or when the high cost of child care forces a day/night shift arrangement on parents).

How does working nights affect the brain?

Unfortunately, the news is not good. We lose the fine-tuning our circadian rhythm provides to keep us well, even if we are frequent night-shifters. It disrupts up to 97 per cent of those genes that depend on our normal body clock, resulting in increased risk of obesity, type 2 diabetes and heart attack.

Deep in the hypothalamus (the area of the brain concerned with regulating our heart rate, hormone production, body temperature, eating, sleeping and wakefulness), we have a ‘sleep ignite’ switch, which ties in with our body clock and once initiated allows us to doze off.

Around 1.5 million Australians are currently employed in shift work (equivalent to 16 per cent of the population). In 2013 Shantha Rajaratnam from Monash University published his findings of a review of the health burden associated with shift work.

Here are some of the key points revealed:

• 32 to 36 per cent of shift workers fall asleep at work at least once a week.
• The risk of occupational accidents is at least 60 per cent higher for non-day shift workers.
• Shift workers have higher rates of metabolic and mood disturbances.
• Shift workers have higher levels of inadequate or poor-quality sleep, insomnia and shift work disorder.

With mounting evidence of the risks of sleep deprivation to the health and performance of shift workers, specific advice has been developed for this group of workers based on regular sleep hygiene principles, but tailored for their particular work environment.

I'm sorry, I can't remember

Sleep is a highly active process. It's the time when we replay the day's events at high speed, consolidating learning and memory, processing our emotions and restoring homeostasis.

Inadequate sleep unsurprisingly interferes with this process. Worse still, it leads to the formation of false memories. Twenty-four hours of sleep deprivation leads to memory distortion, which is worse if we are already sleep deprived.

Getting enough deep sleep is particularly important for forming memory and is especially relevant for young adults. This starts to lessen with age. By middle age, taking a daytime nap can help us protect our memory, as long as we are getting enough sleep at night.

If you or your staff consistently get less than five hours' sleep at night, the risk of forming false memories is far greater. The ramifications of this include increased potential for human error, miscommunication and misinterpretation. It's a far bigger organisational health risk than simply having tired, grumpy coworkers.

If you have something important to remember or learn, the most effective method is to study the material and then sleep for eight hours. Our memory improves when we are offline.

Sleep stability

You may be the most brilliant ray of sunshine on a normal day, but even the sun can be obscured by clouds when it has been shining non-stop for 48 hours straight. In other words, a lack of sleep can make the most even-tempered person … snap.

And then there are those grey clouds. They start to turn a very thundery black. Our negativity bias takes over and we start to interpret information differently. We begin to retain only negative thoughts, and even neutral information takes on less of a ‘unicorns and rainbows’ glow. It's like being permanently wired to an election night special.

Fighting sleep can lead to fisticuffs

Why do we find it so hard to turn our frown upside down when we are sleep deprived, and what impact does it have on us in the workplace? Fatigue leads to increased activation of our brain's flight-or-fight system. As we start to panic or punch, our ability to maintain control of our prefrontal cortex, the conscious thinking part of our brain, is diminished.

The brain's brakes — our mental censor of what we should or shouldn't say and do — is located in the PFC. Without access to that, we become more emotionally unstable, likely to lash out, cry, shout, swear or even become physically aggressive.

This isn't fabulous in private, but in the workplace it can have serious consequences, from loss of job to loss of clients or simply loss of face. As a leader, revealing these symptoms makes you vulnerable to a lack of respect from staff; for a staff member, it makes you vulnerable to a lack of trust from your manager, and to derision from your peers.

Prolonged sleep deprivation leads to a build-up of our stress hormones, including cortisol. In excess this is neurotoxic, and in addition contributes to the vicious circle of sleep deprivation leading to impaired cognition and emotion that leads to further sleep disturbance. It can also contribute to abdominal weight gain, which along with the stress leads to — you guessed it — depression and anxiety.

Insomnia and depression have long been linked. Difficulty in sleeping is often an early sign of anxiety and depression, which will in turn increase stress.

Playing catch-up doesn't work

Busy lives and hectic work schedules can lead to sleep being pared back during the week, so we give ourselves the luxury of a weekend lie-in. Sounds good in theory, but it is actually very hard to claw back that sleep debt adequately in just one or two longer sleeps.

It compounds the problem of poor sleep hygiene, and makes it that much harder to get up on time come Monday morning. So try to stay balanced in your sleep times.

Stay away from the (blue) light

Our technology enables us to stay connected with each other and to do our work far beyond the workplace walls. Many people use their smartphone, laptop or tablet to carry on working in the evening, or even during the night. The problem is these technologies emit a blue light that inhibits the production of melatonin, our sleep hormone.

In his book Night School, Richard Wiseman reveals that the level of sleep deprivation in the UK is far higher than previously estimated, with 59 per cent of the population in 2014 getting less than the recommended seven hours' sleep a night.

His findings also identified a rapid increase in the proportion of people using their smartphone, computer or tablet at night, from 57 per cent in 2013 to 78 per cent in 2014; and most worryingly, 91 per cent of the 21 to 24 age group.

It's recommended that we switch off from all our devices at least two hours before bedtime, or switch to a device, such as a Kindle, that emits a yellow light that has less effect on the brain.

Also, staying attached to our smartphones or tablets keeps us mentally engaged so we find it harder to switch off to relax and go to sleep. This can contribute to daytime sleepiness.

Sleeping on the job: the power of the nap

Some companies have started looking beyond brain and exercise breaks for tired employees. They have naptime as well.

Why?

Because naps can be highly beneficial to brain function, especially if those brains have been working hard over an extended period of time. Studies by Faraut and others report that a 20-minute nap can increase cognitive performance by up to 40 per cent, with the benefit lasting two to three hours.

In researching the impact of sleep on cognition, NASA looked at the role of naps for pilots on long-haul flights. They discovered that pilots allowed to take a 40-minute nap (on average about 26 minutes of actual sleep) increased their median reaction time by 16 per cent. Pilots not allowed naptime experienced a 34 per cent deterioration in reaction time. More worryingly still, they also experienced an average of 22 micronaps lasting between two and ten seconds during the last 30 minutes of the flight! Overall, NASA found that naps of 26 minutes of sleep led to a 34 per cent increase in cognitive performance and a 54 per cent increase in alertness. Now that's impressive.

One major problem with fatigue is that we lose sight of the fact we are tired. Ignoring those warning signs leads to more errors, wandering attention and loss of vigilance to potential danger.

When overtired, the brain starts to insert microsleeps, thought to be the cause of many motor vehicle accidents. A microsleep is a short period when, while appearing to be awake, we are actually asleep for anything from a fraction of a second to up to half a minute. When we are seriously sleep deprived, some of our neurons will go offline, even while the rest of the brain is awake.

A common time to experience microsleep is when you find yourself sitting in a long and boring meeting and you are already tired. In this situation your brain may simply choose to shut down.

Whether or not your company would benefit from introducing naptime will naturally depend on the type of work being done. Where shift work is the norm or where a lot of creative thought is required, naptime can be a blessing.

It can also depend on the culture of the society as a whole. Siesta has a long tradition in those countries where taking a break during the hottest part of the day to sleep and refuel meant workers could work and stay cognitively fresh longer.

With societal change, globalisation and air conditioning, siesta is now less the norm, replaced in some instances by nap bars. In Barcelona, a chain of nap parlours called Masajes a 1.000 was set up in 2000 to provide a mini siesta — a five-minute massage and 30-minute nap.

In Japan, where the population sleeps for half an hour less overall than many other countries, organisations such as Toyota and Okuta Corp have incorporated a power-nap system that allows employees to take a 15- to 20-minute nap.

Google and The Huffington Post have used sleep pods for a number of years now. The pods themselves look futuristic and have a futuristic price tag to go with them. But you don't need a pod to take a nap, just a quiet space where you can dim the light and not be disturbed. Providing for naptime has resulted in increased productivity and a lower error rate, so it seems the pods will be paying for themselves.

Other US companies such as Ben & Jerry's, Procter & Gamble, Cisco, Zappos and Nike are now classified sleep friendly. One poll found around 6 per cent of US companies now provide employee nap rooms.

Helping ourselves to sleep better

Like washing our hands to reduce the risk of transmitting illness, good sleep hygiene allows us to enjoy good-quality, uninterrupted sleep so as to wake refreshed, reinvigorated and ready to face our day.