Focus on Fatigue

Focus on Fatigue, Issue 28: Why do we need sleep?

By January 1, 2015 No Comments

Welcome to Focus on Fatigue,

Welcome to the first Focus on Fatigue for 2015. We hope that you have enjoyed the recent holiday season and are now rested and ready to tackle the year ahead.

Here at Focus on Fatigue we’ve decided to get back to basics and explore some of the issues underlying the need for Fatigue Risk Management. In the coming months we will be covering issues such as how much sleep we actually need, the best ways to achieve our ‘sleep number’ and other topics relevant to users of FAID.

We all spend approximately one-third of our lives sleeping, and this month we will look at the question that philosophers and researchers alike have been attempting to answer for hundreds of years: Why?

We hope that you’ll enjoy our exploration of this and other issues. After a good night’s sleep, of course!

The FRMS Team

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InterDynamics Pty Ltd
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Views expressed in articles and links provided are those of the individual authors, and do not necessarily represent the views of InterDynamics (except where directly attributed).

Feature Article

Sleep? Who needs it?

How often do you hear friends or colleagues make the following statement:

“I’m so busy lately that I’ve really had to cut back on eating to make time for everything else. I’m hardly getting any food at all!”

The answer is probably, ‘Never!’ Everyone knows that we cannot function properly without food. But the truth is that humans can live longer without food than we can without sleep, and yet few of us think much of cutting back on sleep when life starts to get hectic and we have trouble keeping up.

“I’m hardly getting any sleep at all!”

Now there’s a phrase that many of us hear often – sometimes coming from our own mouths!

What is sleep anyway?

Researchers all over the world have spent many years trying to figure out exactly what sleep is – with little success.

The Macquarie Dictionary defines sleep as ‘to take the repose or rest afforded by a suspension of the voluntary exercise of the bodily functions and the natural suspension, complete or partial, of consciousness.’

As humans, we have always seemed to have a love/hate relationship with sleep. English writer, Thomas Dekker, described sleep as ‘the golden chain that ties health and our bodies together,’ while Virginia Woolfe called it ‘the deplorable curtailment of the joy of life.’

But if there is one certainty in life, it is that we must all sleep. Right?

Do we really need to sleep?

For many years, people have been asking the question, ‘Do we really have to sleep? Can’t we just skip it?’

In 2008 two researchers (Cirelli & Tononi, 2008) examined all the evidence that has been collected on the subject and decided that the answer is a resounding, ‘Yes!’ Sleep is absolutely essential. They based their answer on three factors:

  • There is no convincing case of a species that does not sleep.
  • There is no clear instance of an animal that forgoes sleep without some compensatory mechanism.
  • There is no indication that one can truly go without sleep without paying a high price.

Of course, the next question we all ask is, ‘Why do we have to sleep? What does it do for us?’

Why do we need sleep?

Scientists have examined this question from many angles. (Havard Medical School, 2007) Unfortunately, despite decades of research, and many discoveries about varying aspects of sleep, a definitive answer to this particular question is still in the works. There are many theories, such as:

  • The energy conservation theory – We use less energy when we sleep. Not only do we stay still, but our metabolism and body temperature both drop as well. This would suggest that a major function of sleep is the conservation of energy. (Siegel, 2005)
  • Restorative theories – Sleep allows the body time to repair and rejuvenate itself. In fact many major restorative functions, such muscle growth, tissue repair and the release of growth hormones occur mostly during sleep (Siegel, 2005; Frank, 2006)
  • Brain plasticity theory – Recent studies have found a correlation between sleep and changes to the structure and organisation of the brain. This phenomenon is known as brain plasticity. It helps us to do things like process memories. (Frank, 2006)
  • Brain maintenance – Recent research (conducted on mice) has suggested that sleep may allow the brain to flush out potentially neurotoxic waste products that accumulate in the central nervous system when we’re awake. (Xie, 2013)

There is no escaping the need for sleep

The truth is that we are still learning about why we have this need for sleep, but we do know that it is essential, it is undeniable. It is one of the essentials for human life, along with food, water and breathing. As much as we sometimes like to deny it, sleep is not an optional extra.


  • Cirelli, C. & Tononi, G. (2008) Is sleep essential? Plos Biology, 6(8), e216.
  • Frank, M. G. (2006) The mystery of sleep function: Current perspectives and future directions. Reviews in the Neurosciences, 17 (4), 375-392.
  • Siegel, J. M. (2005) Clues to the function of mammalian sleep. Nature, 437(7063), 1264-1271.
  • Why do we sleep, anyway? (2007) Harvard Medical School. Retrieved 6 June 2013 from
  • Xie, L., Kang, H., Xu, Q., Chen, M. J., Liao, Y., Thivagarajan, M., O’Donnell, J., Christensen, D. J., Nicholson, C., Iliff, J. J., Takano, T., Deane, R., and Nedergaard, M. (2013) Sleep drives metabolite clearance from the adult brain. Science, 342(6156), 373-377.

InterDynamics News

Conferences and presentations

This section outlines recent and upcoming InterDynamics’ speaking engagements and/or conferences that we recommend and will be attending.

9th International Conference on Managing Fatigue, Freemantle Western Australia, 23-26 March 2015

The ‘Managing Fatigue’ conference series is now an established and respected forum for research updates and discussion in the fatigue management community. First convened in 1992 by Associate Professor Laurence Hartley the meeting was most recently held in Freemantle in 2011. Each conference has primarily focused on the effects of fatigue in the transportation sector and this has involved working in conjunction with organisations such as the ‘National Road Transport Commission’ (NRTC) and the ‘Australian Transport Safety Bureau’ (ATSB). Over the years the meeting focus has also evolved to encompass a wider arena including sectors such as Aviation, Maritime, Industrial, Resources and Health.

Conference Themes:  Transportation, Resources, and Health

Who Should Attend?:  Occupational Health and Safety Professionals,  Transportation Staff, Researchers, Road Safety Experts, Military Personnel, Aviation Experts, Freight and Heavy Vehicle Professionals, Defence, Science and Technology Organisations, Medical Professionals, and Road Authorities


Two important reasons for our need to sleep are explained the following short videos.

Brain plasticity

The benefits of sleep: What’s really going on when your body is at rest

Shai Marcu, Educator, TED-Ed, “The benefits of sleep: What’s really going on when your body is at rest” ( January 2015

It’s 4am, and the big test is in 8 hours. You’ve been studying for days, but you still don’t feel ready. Should you drink another cup of coffee and spend the next few hours cramming? Or should you go to sleep? Shai Marcu defends the latter option, showing how sleep restructures your brain in a way that’s crucial for how our memory works.

More …

Brain maintenance

One more reason to get a good night’s sleep

Jeff Iliff, Neurscientist, Ted Talks, “One more reason to get a good night’s sleep” ( September 2014

The brain uses a quarter of the body’s entire energy supply, yet only accounts for about two percent of the body’s mass. So how does this unique organ receive and, perhaps more importantly, rid itself of vital nutrients? New research suggests it has to do with sleep.

More …


In the second video, Jeff Iliff talks about research he was involved in which found that the sleeping brain is hard at work cleaning itself. Following is the abstract for that important piece of research.

Xie, L., Kang, H., Xu, Q., Chen, M. J., Liao, Y., Thivagarajan, M., O’Donnell, J., Christensen, D. J., Nicholson, C., Iliff, J. J., Deane, R., and Nedergaard, M. (2013) Sleep drives metabolite clearance from the adult brain. Science, 342 (6156), 373-377.

The conservation of sleep across all animal species suggests that sleep serves a vital function. We here report that sleep has a critical function in ensuring metabolic homeostasis. Using real-time assessments of tetramethylammonium diffusion and two-photon imaging in live mice, we show that natural sleep or anesthesia are associated with a 60% increase in the interstitial space, resulting in a striking increase in convective exchange of cerebrospinal fluid with interstitial fluid. In turn, convective fluxes of interstitial fluid increased the rate of β-amyloid clearance during sleep. Thus, the restorative function of sleep may be a consequence of the enhanced removal of potentially neurotoxic waste products that accumulate in the awake central nervous system.

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