Why is Sleep so Important?
How Much Sleep Should You Have?
As with many things this varies from individual to individual. One person may swear on that magical 8 hours, whereas another may fully function with 6 and another may not feel fully rested until they’ve hit 9 hours.
As long as you feel refreshed and alert the next day you’re probably sleeping enough - as always, it’s an individual marker for you, which you should try to work out and achieve.
The Stages of Sleep
Sleep is more than just our brain shutting down, it also involves an active state. When we sleep, we go through 2 main phases of sleep: rapid eye movement sleep (REM) and non-rapid eye movement sleep (non-REM).
With these two phases, you go through a cycle moving between non-REM and into REM sleep and back into non-Rem and so on (Bupa, 2015).
Non-REM sleep is broken up into two parts: light sleep; and deep/low-wave sleep. So, what do these two mean and what does REM sleep mean?
Stage 1: Light sleep in non-REM: the first stages of sleep, which begins when you start to feel drowsy. When you fall asleep, this leads to a decrease in your heart rate, decrease in body temperature and your muscles relax. At this stage, it is easy for you to be woken up. It is also the time where you can experience the sensation of starting to fall and then sudden muscle contractions occur, known as hypnic jerks, something that you may have experienced.
Stage 2: Deep/slow-wave sleep in non-REM: this is the stage where you begin to sleep more heavily and your blood pressure decreases. Eye movement ceases and brain waves are slower. This is the stage most associated with sleep walking and/or talking. You are harder to wake up and if you are, you will most likely feel confused.
Stage 3: REM sleep: this is the phase where your brain is more active and where you experience your eyes moving rapidly from side to side. Your heart rate, blood pressure, and breathing rate increases, however, the rest of your body remains relaxed. This phase is where you dream. It is usual to enter REM sleep around 90 minutes after you fall asleep and adults will usually experience 5-6 REM cycles each night (Sleep.org, 2017).
What happens, however, when we deprive ourselves of sleep and reduce the amount of time we spend resting in the sleep cycle? How important is sleep for our health?
When we have a good night’s sleep, it aids with improving our learning and problem-solving skills. This also improves our ability to make decisions, pay attention and even be creative (National Heart, Lung, and Blood Institute, 2017). I’m sure most of us have experienced a time where we have felt tired and unable to concentrate on what we were meant to be doing. This feeling of fatigue leaves us feeling a bit foggy in the head, which impacts how well we can concentrate and even learn. It can even impact our mood, leaving us feeling agitated and grumpy. Not getting enough sleep and becoming deficient in sleep has also been associated with depression and a lack of motivation (National Heart, Lung, and Blood Institute, 2017).
Sleep restriction for over 14 nights led to an impairment in neurobehavioral functions, without the individuals realizing they were experiencing these deficits (Van Dongen et al., 2003), similar to the effects of 2 nights of total sleep deprivation. Neurobehavioral functions include: alertness; sustained-attention reaction time; working memory; and mental arithmetic.
It has been found that driving while drowsy, due to being sleep deprived, has a similar effect on our body as drinking alcohol. This impacts on how quickly we make decisions and act upon those decisions (Sleep Foundation, 2016).
When looking at heart health, we look at cardiovascular disease (CVD). This is for all diseases of the heart and the circulation around it, including heart disease, stroke, heart failure, coronary artery disease, peripheral arterial disease and aortic disease. Those who are sleep restricted are at a higher risk of cardiovascular disease.
It has been found in a study on 3000 adults, ages 45+, that those who slept less than 6 hours a night, were twice as likely to have a stroke or a heart attack, than those who got 6-8 hours (National Sleep Foundation, 2017). In a meta-analysis, it has also been found that both short and long durations of sleep are predictors of cardiovascular outcomes (Coronary heart disease, stroke, and total CVD) (Cappuccio et al., 2011)
There is a relationship between inflammation and cardiovascular disease. When we sleep, markers which indicate inflammation in are body are at their lowest, so when sleep duration is shortened this leads to elevation of these markers (Mullington et al., 2009). These inflammatory markers don’t just impact our heart health but cause inflammation to the body as a whole, including our gastrointestinal health and how well our immune system responds to infections and illness (Irwin, 2015).
Making sure we get an adequate amount of sleep is also important for our bone health. When individuals experienced a decrease in their sleep duration or restriction, it lead to a decrease in bone mineral density (Fu et al., 2011 and Endocrine Society, 2017).
However, it has also been found in middle-aged and elderly women that prolonged sleep duration of more than 8 hours per day was associated with a higher risk of osteoporosis (Moradi et al., 2017). In children and teens, deep sleep has been shown to cause the hormone that promotes normal growth, involved in healthy growth and development. This hormone also helps promote muscle mass and repair cells and tissues in children, teens and adults (National Heart, Lung, and Blood Institute, 2017).
Metabolic syndrome is a where metabolic risk factors all come together. This includes obesity; insulin resistance; pro-inflammatory state of the body; hypertension (high blood pressure); hypertriglyceridemia; and low levels of high-density lipoprotein (Diabetes.co.uk, 2017).
A meta-analysis found that in both men and women, a short sleep duration was associated with an increased risk of metabolic syndrome. Whereas a long sleep duration was not associated with an increased risk (Xi et al., 2014).
In women aged around 20 years of age, it was found that when they had consistent sleep patterns and a sufficient amount of sleep, this lead to a lower body fat level being found. Those who were sleeping less than 6.5 hours or over 8.5 hours and with a poor quality of sleep were found to have an association between sleep and a higher body fat level. This concluded that both the quality of sleep and also the consistency at which we go to bed and rise in the morning, impacts body fat levels (Bailey et al., 2014).
It has been found in other research that when we endure inconsistent sleep-wake patterns, it is associated with an increase in fat mass (Kim et al., 2015). In adults, it has been seen to be more of a ‘U’ shape association, where short (deprived) sleep and prolonged sleep were both associated with an increased risk of becoming overweight/obese (Fatima et al., 2015).
The amount of sleep we get as teenagers can also increase our risk of becoming obese. Short sleep duration (under 6 hours) in adolescents (mean age of 16), was associated with an increase in rates of obesity in both males and females by the time they were going into young adulthood (mean age 21) (Suglia et al., 2014).
Furthermore, a meta-analysis confirmed this report, by finding that those who were subjected to a short sleep duration (less than 6 hours), had twice the risk of being overweight/obese, than those sleeping for a long duration, agreeing that sleep duration in young individuals is significantly associated with their future risk of becoming overweight/obese (Fatima et al., 2015).
This demonstrates that throughout our lifecycle, sleep is an important factor that we may forget when trying to maintain our weight. One of the theories about why sleep impacts our weight is that, due to the shorter sleep duration, individuals may feel fatigued during the day and therefore reduce the amount of physical activity they do to compensate for this.
It has also been found that when we sleep for a short duration, it may lead to an increase in our energy intake but decrease our energy expenditure, due to its impact on some of our hormones. It suppresses the hormone leptin and stimulates the hormone ghrelin. When our body releases the hormone leptin, it is indicating that we are satiated and therefore food intake should be reduced. Whereas ghrelin, is secreted by the stomach and stimulates our appetite (Copinschi, 2005. And Schmid et al., 2008).
If you're finding it hard to sleep, it's worth making some freezable meals to have to hand to ensure you're still eating nourishing and nutritious meals.
So, how many hours do I need?
For adults, it is recommended that we get around 7-8 hours of sleep a night. In teenagers around 9 hours, however, they tend to have disrupted sleep, due to their irregular sleeping patterns, staying up late and sleeping in at the weekend. This can impact and disrupt their quality of sleep.
It has been found that one in three of us suffer from poor sleep, with different factors playing a role including stress; use of technology; and taking work home being the usual suspects (NHS Choices, 2015).
It appears that worldwide, more and more people are experiencing chronic sleep deprivation. It’s normal to wake up during the night briefly, however if you, over a period of time, lose out on sleep (if you have been deprived), you will build up what is known as ‘sleep debt’ which eventually you’ll need to restore through sleep.
Making sure that you get a good night’s sleep, plays an important role in so many areas in regards to health.
As we are all individuals, we all require a different amount of sleep but it’s important to try and work out whether you are getting enough sleep, or is tiredness impacting your life?
I hope you have enjoyed this blog.
Daisy, MSc PGDip ANutr,
Is a Registered Associate Nutritionist with a Master's Degree in Public Health Nutrition, and a Post Graduate Diploma in Eating Disorders and Clinical Nutrition, both of which are Association for Nutrition (AFN) accredited. She, also, has a BSc degree in Psychology and Cognitive Neuroscience; and has completed an AFN accredited Diet Specialist Nutrition course. Daisy has worked for an NHS funded project, the Diabetes Prevention Programme; and shadowed a nutritionist in Harley Street, London
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