In today’s hectic society, sleep may feel like a luxury when in fact it is a necessity.
Sleep is crucial to health, safety and overall wellbeing. It’s still a bit of a mystery why it is so important, but most experts agree that sleep is the time when your brain recharges, allowing it to catalogue the previous day’s experiences, learn and make memories. Sleep also triggers the release of hormones that regulate energy, mood and mental acuity, is the time when cellular damage is repaired and when toxins are removed that accumulate during the day. Not getting enough has been linked to problems with mood and relationships and poor work performance - creativity, productivity and concentration all take a hit when you fall short. Lack of sleep also raises the risk of high blood pressure, heart disease, diabetes, obesity, depression, stroke and even car accidents.
In this article we shed a bit more light on this often elusive but always essential, primal need to sleep. We look at the sleep cycle in a bit more detail and share with you a great resource that shows how much sleep you need at each stage in your life. We also find out why some people (think Margaret Thatcher) simply don’t fit into that eight-hour box, why you feel achy when you wake up after a disturbed night and how a lack of sleep can get in the way of weight loss.
Want to know more about this fascinating topic? Read on…
There are five stages in a healthy sleep cycle. A complete cycle takes an average of 90 – 110 minutes as you pass through stages 1 - 4 and then finally to REM (rapid eye movement) sleep and then back to stage 1. This continues cyclically through each night and you’ll generally go through 3 – 4 of these cycles per night. Sleep cycles earlier in the night tend to have shorter REM sleep stages and longer periods of deep sleep, whereas later in the night, REM sleep time increases and deep sleep time is shorter.
Stage 1 (Light sleep): This is the stage where you drift in and out of sleep and can easily be woken. Eye movements and muscle activity slow down and many people experience sudden muscle contractions during this stage.
Stage 2 (Light sleep): There is no eye movement in this stage. Brain waves are generally slower and there is an occasional burst of rapid brain waves. You become increasingly unplugged from the world during stages 1 and 2.
Stage 3 (Deep sleep): Extremely slow ‘delta’ brain waves interspersed with smaller faster brain waves characterise stage 3 as you enter deep sleep. During stages 3 & 4, both brain and body activity drop to their lowest point.
Stage 4 (Deep sleep): Delta waves are produced almost exclusively in stage 4. There is no eye movement or muscle activity during stages 3 & 4. It’s very difficult to wake someone when they are in deep sleep; this is often the period of the sleep cycle when children may experience night terrors, bedwetting and sleepwalking.
Deep sleep is essential for physical regeneration, growth and hormonal regulation. Without deep sleep, you’re more likely to become ill, gain weight and feel depressed.
(Stage 5) REM sleep: Eyes move rapidly, limb muscles are temporarily paralysed and breathing is more irregular, rapid and shallow. Also, heart rate increases, blood pressure rises and body temperature regulation is inhibited. Your brain becomes busily active during REM phase, even more than when you are awake. Most dreams occur during REM sleep too and you will usually only remember them if you wake during this stage. Most people have 3 – 5 phases of REM sleep per night. Infants spend nearly half of their sleep time in REM, whereas for adults only about 20% of sleep time is in REM. As you age, you spend progressively less time in REM sleep.
REM sleep is essential for the brain to process and synthesise memories and emotions, activity that is crucial for learning and higher-level thought. A lack of REM sleep results in slower cognitive and social processing, problems with memory and difficulty concentrating.
How much sleep do you need?
Babies, children and teens need significantly more sleep than adults to support their rapid mental and physical development and most people will need less sleep as they get older. This chart, which has been compiled by the National Sleep Foundation, gives an overview of the average amounts of sleep needed at different stages throughout your life. It is a useful starting point to see if you’re getting enough.
Your sleep pattern is unique to you
As with all things health, there’s individual variation in sleep habits to consider too. Margaret Thatcher famously thrived on just 4hrs a night, as does Yahoo’s CEO Marissa Meyer. Richard Branson and PepsiCo’s Indra Noovi both get around 5hrs a night. At the other end of the spectrum, singer Mariah Carey says she needs a solid 15 hours to feel alive and refreshed the next day!
Can a genetic mutation make you sleep less?
In 2009, a team of researchers led by Ying-Hui Fu at the University of California, San Francisco, uncovered a tiny genetic mutation that might help to explain why some people can not only survive, but actually seem to thrive on very short sleep1. Fu and her colleagues compared the genetic profiles of different members of the same family who all regularly got around 4hrs sleep, yet woke feeling refreshed and completely alert. They discovered a tiny mutation in a gene called DEC2; this mutation was present in the family members who were short sleepers, but not in those who slept a more normal 8hrs, nor in 250 unrelated volunteers. The team then bred mice with the same genetic mutation. These mice slept less but performed just as well as mice without the mutation, when given physical and cognitive tasks. For most people, getting 4hrs sleep a night would be detrimental to health, however this mutation may help to explain why this isn’t the case for everyone.
Fu commented on the results,
“Clearly people with the DEC2 mutation can do the same cleaning up process in a shorter period of time – they are just more efficient than the rest of us at sleeping.”
Whilst charts that detail optimal sleep times can be useful, it’s key to get to know your own body and what works for you. Independent sleep consultant Neil Stanley said,
“If we could all figure out what kind of sleeper we are, and live our life accordingly, that would make a huge difference to our quality of life.”
How lack of sleep causes weight gain
According to research carried out by the National Sleep Foundation in 2008, people who sleep less than 6 hours each night on weekdays are significantly more likely to be obese than those who sleep 8 hours or more2.
In a review article published in the European Journal of Endocrinology in 2008, researchers looked at the links between chronic partial sleep loss and an increased risk of weight gain and obesity. The review article looks at how poor sleep results in increased hunger and appetite and many metabolic and endocrine alterations, including decreased glucose tolerance, decreased insulin sensitivity, increased evening cortisol, increased levels of ghrelin and decreased leptin. Leptin and ghrelin are two important hormones that shape appetite and hunger signals3.
In a more recent study carried out by the University of Chicago and published in the March 2016 issue of Sleep, researchers looked at how sleep and weight gain interact biologically4. They found that sleep deprivation affects the body in a similar way to activation of the endocannabinoid (eCB) system, most well-known for being activated by chemicals found in marijuana, and crucial in the brain’s regulation of appetite and energy levels. The eCB system affects the motivation and reward circuits in the brain and can spark a desire for tasty foods.
In the study, researchers recruited 14 healthy, non-obese people (11 men and 3 women) between the ages of 18 and 30. They were placed on a fixed diet and allowed either 8.5hrs sleep or a restricted 4.5hrs of sleep for 4 nights. All study participants followed both sleep conditions in a controlled clinical setting, and with a break of 4 weeks between each phase. Blood samples were collected at the beginning of the afternoon on the third day of the study. They found that sleep deprived participants had higher and longer-lasting eCB levels in the afternoons than when they’d had a full night’s rest and this coincided with reported increases in hunger and appetite.
The study participants all had an evening meal on the fourth day and then fasted until the next afternoon. At this point they were allowed to choose their own food and drinks for the rest of the day. Under both sleep conditions all participants consumed about 90% of their calories at their first meal. However those who were sleep deprived consumed more and unhealthier snacks in between meals. Results showed that this is the point at which eCB levels were at their highest, suggesting that higher eCB levels caused by lack of sleep were driving hedonic, or pleasurable, eating.
Lead researcher, Dr Erin Hanlon commented that if you see unhealthy food and you’ve had optimal sleep, you may be able to control parts of your natural response. “But if you’re sleep deprived, your hedonic drive for certain foods gets stronger, and your ability to resist them may be impaired. So you are more likely to eat it. Do that again and again, and you pack on the pounds.”
Why a lack of sleep leaves you feeling achy the next morning
So we know that a lack of sleep can lead to weight gain and many other health problems, but why do you often feel achy and tender when you wake after a disturbed night’s sleep? New research published in the September 15th issue of Biological Psychiatry and carried out by the UCLA Cousins Center research team has found that losing sleep for even part of one night can trigger a key cellular pathway that produces tissue-damaging inflammation5.
In the study, researchers measured levels of nuclear factor (NF)-kB – an important marker of inflammation. Levels were measured in the morning after normal sleep, after partial sleep deprivation and after a recovery sleep. Activation of the inflammatory marker was significantly greater after partial sleep deprivation than after baseline or recovery sleep.
John H Krystal M.D., editor of Biological Psychiatry and affiliated with both Yale University School of Medicine and the V.A. Connecticut Healthcare System commented on the results,
“The closer that we look at sleep, the more that we learn about the benefits of sleeping. In this case, Irwin and colleagues provide evidence that sleep deprivation is associated with enhancement of pro-inflammatory processes in the body.”
Want to improve your sleep? Here’s what to do next…
Whilst a few people may be able to thrive on a mere 4hrs a night, it’s clear that for the rest of us, 8 hours is far more beneficial, and that babies and growing children need much more. Chronic lack of sleep is associated with a myriad of health problems and everyone’s short and long-term health would benefit from getting regular good sleep. If you’ve been inspired to take action, read our expert psychologist and nutritionist tips for getting a better night’s sleep. And if you fancy giving something completely new a try, have a go at this recipe for ‘banana tea’ – apparently it works a treat!
1. Fu YH, He Y et al. The transcriptional repressor DEC2 regulates sleep length in mammals. Science 2009. Aug 14; 325(5942): 866-70. doi: 10.1126/science. 1174443
2. National Sleep Foundation. Sleep in America Poll. National Sleep Foundation; Washington, DC: 2008.
3. Van Cauter E and Knutson KL. Sleep and the epidemic of obesity in adults and children. Eur J Endocrinol. 2008 Dec; 159 (S1): S59-S66 doi: 10.1530?EJE-08-0298
4. Hanlon EC, Tasali E et al. Sleep Restriction Enhances the Daily Rhythm of Circulating Levels of Endocannabinoid 2-Arachidonoylglycerol. Sleep. 2016 Mar 1;39(3):653-64. doi: 10.5665/sleep.5546. PMID: 26612385.
5. Irwin MR, Olmstead R. Sleep disturbance, sleep duration and inflammation: a systematic review and meta-analysis of cohort studies and experimental sleep deprivation. Biol Psychiatry. 2016 Jul 1; 80(1): 40-52. doi: 10.1016/j.biopsych.2015.05.014. Epub 2015 Jun 1
National Sleep Foundation www.sleepfoundation.org