The Importance of Sleep for Health and Wellbeing

Not every article here at Fitness Savvy is going to be War and Peace! However, while considering the importance of sleep we decided to keep this one short and simple so you can get yourself tucked up in bed for a cosy and relaxing 8-hour nap – you’re welcome!

A Decent Nights’ Sleep Improves Cognitive Function

Cognition – as described by the Oxford English Dictionary is:

“The mental action or process of acquiring knowledge and understanding through thought, experience, and the senses”1

Basically, just about everything you do relies on proper cognitive function – attention, memory, reasoning, judgement, decision making – to name a few. Have a poor nights’ sleep and see how well you function the next day… We’ve all been there – you’re forgetful, make silly decisions and your judgement is shot to bits. However, let’s not simply rely on our own experiences – after all, we may have been tired and not functioning well enough to make proper judgement as to whether our cognitive function was impaired or not! So for that reason, we are going to refer to hard scientific fact to make the point. A study by Saadat et al., 20162 looked at the effects of sleep deprivation on anesthesiologists. The study found tension, anger, fatigue, confusion, irritability and sleepiness to be significantly affected, as well as a marked decrease in vigor, energy, and confidence. The study concluded that partial sleep deprivation affected the total mood status of anesthesiologists and impacted their cognitive skills.

Quality Sleep Reduces Muscle Atrophy

This is the most important one when looking to build and maintain muscle  – so pay close attention! Sleep regulates hormones – including growth and stress hormones. Studies have shown an increase in cortisol (the stress hormone) secretion, and a reduction in testosterone and Insulin-like Growth Factor 13 – a lethal cocktail of doom for your muscles.

We could go on for hours citing studies that support the importance of sleep for proper hormonal function, but we will just refer to one more for good luck: Results from a 2004 study4 found that concentrations of plasma growth hormone (as its name suggests, promotes cell growth), IGF-I (Insulin-like growth factor, which encourages skeletal muscle hypertrophy by inducing protein synthesis and blocking muscle atrophy) prolactin (a protein influential in over 300 separate processes in various vertebrates, including humans), and leptin (a hormone which inhibits hunger) were all suppressed by sleep deprivation. So basically you don’t grow muscle and end up eating more. What a combo, right?

Proper Sleep Improves Insulin Resistance

Insulin sensitivity plays an important role in metabolic functions. Obesity is associated with poor insulin sensitivity, whereby the pancreas secretes higher levels of the hormone to regulate blood sugar levels. Lower sensitivity means a higher level of insulin is released into the blood. Insulin initiates a signal transduction which increases glucose uptake from the blood into fat, liver and skeletal muscle cells. Poor sleep = lower insulin sensitivity. Lower insulin sensitivity = higher levels of insulin. Higher insulin levels = greater storage of glucose – which in most cases ends up as fat. After a resistance training session, high insulin levels can be a good thing; this is because muscle contraction causes cells to bring GLUT4 receptors (little taxis for glucose) to their surfaces, and so glucose is absorbed by the muscle instead. This is great, because once stored in the muscle cell as glycogen, it is not able to be released back into the blood stream to be used as energy elsewhere, so will be used exclusively by the muscle cell when training. However, for the most part, glucose is going to be stored in fat cells. Not what we want at all. We mentioned Leptin in the previous point – a hormone which suppresses hunger… well, to make matters worse, the appetite-stimulating hormone ghrelin increases, too.5

Happy from Sleep

You Are Happier When You Sleep Well

Are teenagers grumpy because they are teenagers, or are they just not understanding the importance of sleep? That age old question that everyone ponders at some point in their lives. Well here we have the answer: it’s because they’re probably not getting enough sleep. Whether it’s staying up late playing video games, cramming for exams or simply beginning the new series of their favourite television show with the intention of going to sleep after “one episode”, and accidentally watching all 10 – there is no escaping the fact that this lack of sleep is effecting their moods. Before we continue, let’s cast aside our preconception that all teenagers are moody and let science do the talking for a minute of two. In a study looking at sleep deprivation in relation to mood in adolescents6 it was concluded that sleep loss can “causally affect mood states in healthy adolescents, with females having heightened vulnerability”. A separate study7 concluded that:

“After only a few days of shortened sleep, at a level of severity that is experienced regularly by millions of adolescents on school nights, adolescents have worsened mood and decreased ability to regulate negative emotions.”

But it’s not just teenagers who are at risk of being grumpy after a poor nights’ sleep. We are all susceptible. These studies were conducted after a clear link had already been established between poor sleep and mood in adults.

Sleep Aid Supplements

Longer Sleep Duration Reduces Your Risk of Developing a Cold

If you are one of those people who always seems to have a cold – maybe (rather than sheer bad luck) it’s down to your sleeping pattern. Participants in a 2009 study with less than 7 hours of sleep were 2.94 times more likely to develop a cold than those with 8 hours or more of sleep.8 And if that wasn’t enough to convince you (you cynical bunch), then cop a load of this: For some strange reason, 164 healthy men and women (aged 18 to 55) volunteered for a study whereby they were administered nasal drops containing – of all things – the bloody rhinovirus!9 Now call me old fashioned, but I always thought nasal drops were to relieve symptoms of colds and flu. Oh well, I guess you learn something new every day! Anyway, these rather peculiar individuals who voluntarily chose to be infected were kind enough to keep sleep diaries. Those sleeping less than five hours were shown to be at greater risk of developing the cold than those sleeping more than seven hours per night.

Edd’s Final Words

So there you have it – the importance of sleep, backed up by science and hard-core facts: Miss out on a decent nights’ sleep and expect to receive the full wrath of every germ going, prepare your friends and family for the moodier version of you, don’t count on remembering where you put your car keys, accept that you probably wasted away some muscle mass, and don’t say you weren’t warned! Over and out!


  1. Oxford Dictionary Definition
  2. Saadat et al., Time to talk about work-hour impact on anesthesiologists: The effects of sleep deprivation on Profile of Mood States and cognitive tasks. Paediatr Anaesth. 2016 Jan;26(1):66-71.
  3. Dattilo et al., Sleep and muscle recovery: endocrinological and molecular basis for a new and promising hypothesis. Med Hypotheses. 2011 Aug;77(2):220-2.
  4. Everson CA, Crowley WR. Reductions in circulating anabolic hormones induced by sustained sleep deprivation in rats. Am J Physiol Endocrinol Metab. 2004 Jun;286(6):E1060-70. Epub 2004 Feb 10.
  5. Morselli L, Leproult R, Balbo M, Spiegel K. Role of sleep duration in the regulation of glucose metabolism and appetite. Best Pract Res Clin Endocrinol Metab. 2010 Oct;24(5):687-702.
  6. Short MA, Louca M. Sleep deprivation leads to mood deficits in healthy adolescents. Sleep. 2015 Nov 1;38(11):1823-6.
  7. Baum KT, Desai A, Field J, Miller LE, Rausch J, Beebe DW. Sleep restriction worsens mood and emotion regulation in adolescents. J Child Psychol Psychiatry. 2014;55(2):180-90.
  8. Cohen S, Doyle WJ, Alper CM, Janicki-Deverts D, Turner RB. Sleep habits and susceptibility to the common cold. Arch Intern Med. 2009 Jan 12;169(1):62-7.
  9. Prather AA, Janicki-Deverts D, Hall MH, Cohen S. Behaviorally Assessed Sleep and Susceptibility to the Common Cold. Sleep. 2015 Sep 1;38(9):1353-9.


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