Why Do We Need Sleep?

11 July, 2011

“Sleep is the golden chain that ties health and our bodies together.” Thomas Dekker – The Guls Horne Book, 1609

The conundrum has baffled scientists for years, but researchers are still not clear about the details of the function of sleep.  Some believe that it is an energy-saving device, built into our DNA.  But in truth, a night’s sleep only saves us about 50kCal, so the effects on energy consumption are negligible.

What is clear is that while we sleep, a great deal of repair and brain development goes on.  Sleep is vital for maintaining normal levels of cognitive skills such as memory and speech.  Growth hormone is also secreted while we sleep, triggering protein synthesis, the repair and restoration of muscle and other tissues.

Interestingly, in dream sleep, the brain is actually very active.  Whilst we are not sure what function dreams play, it is possible that they serve to reorganize and order information that has been harvested by the brain during the day.

One way in which we get a clue as to the purpose of sleep is to look at what happens if you don’t get enough.  Cognitive functions, including memory, face-recognition, speech and problem-solving, are significantly impaired, and we are likely to be irritable and uncommunicative.

Our coordination also suffers, and we perform familiar tasks with less agility.  Working with machinery or driving a car may become hazardous.  In fact, 17 hours of sleep deprivation is equivalent to a blood alcohol of 0.05%, which is the legal alcohol limit in the UK.

According to the National Highway Traffic Safety Administration (NHTSA) there are approximately 100,000 crashes a year in the U.S. that are caused by drowsy driving. Approximately 71,000 people are injured as a result of drowsy driving.  Some 1,500 die.

In the UK, according to research conducted by Loughborough University, some 20% of all motorway traffic accidents are sleep-related vehicle accidents (SRVA) and are dramatically compounded by even low levels of alcohol intake.  Driving when tired can literally be lethal!

Many accidents at work can also be linked to sleep problems.  A 1996 study concluded that the following major accidents were all associated with sleep deprivation of the personnel involved:

    1. Exxon Valdez oil spill in Prince William Sound, Alaska in 1989, considered to be one of the most devastating disasters caused by humans in history, eventually covering 1,300 miles of coastline.  The spill was responsible for the deaths of perhaps as many as 250,000 seabirds, at least 2,800 sea otters, 247 bald eagles and billions of salmon eggs.  At the time of the accident, the captain of the tanker was down below, sleeping off a drinking binge.


    1. The space shuttle Challenger tragedy in 1986.  73 seconds into mission 51L, the shuttle exploded, killing all on board.  The mission was problematic from the start, and crews had been working round the clock to solve technical issues which repeatedly delayed lift-off.  Some commentators have implicated bad decision-making as a result of sleep deprivation to be a cause of missing the faulty O-ring which was responsible for the explosion.


  1. The nuclear accident at Chernobyl Nuclear Power Plant, also in 1986 in which an explosion and fire released radioactive gasses across much of Western Russia and Europe.  The battle to contain the disaster ultimately involved over half a million workers.  At least 31 deaths have been directly attributed to the disaster, but an additional million could be attributed to radioactive contamination as a result of the event.  Engineers who had been at work for 13 hours or more at the time of the accident had totally missed or were confused by warning signals on their control panels.

The nuclear accidents at the Three Mile Island and Peach Bottom reactors have also been associated with sleep deprivation of the personnel involved.

Evidence collected from studies on animal sleep in recent years has shown the dramatic effects of sleep deprivation on the immune system.  Animals deprived of sleep altogether lose all immune function and die in a matter of weeks.

Sustained lack of proper sleep in humans can hugely impact our health, leading to long-term health consequences and even lower life expectancy.  Obesity, diabetes, heart disease and high blood pressure can all be linked to sleep deprivation.

Conversely, sleep contributes to improved ability to fight disease, better muscle tone and even healthier-looking skin.  We perform tasks more accurately, look fresher, think more clearly, make more appropriate judgments and behave better.

So if we feel more alert, more energetic, rejuvenated, happier and better able to function after a good night’s sleep, why on earth would we deprive ourselves of this wonderful and mysterious gift?

Surely it would be more productive to cherish the benefits of sleep and put a little effort into reorganizing our lives and lifestyles to improve the quantity and quality of this most natural of functions.

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