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.
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?
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).
Lack of sleep can affect your mood
It has been found that when healthy adults are restricted to sleep periods of 6 hours or less per night, for 14 consecutive nights, it led to cognitive performance deficits, similar to that of 2 nights of total sleep deprivation. This lead to an impairment in neurobehavioural functions, without the individuals realising they were experiencing these deficits (Van Dongen et al., 2003). Neurobehavioural functions include: alertness; sustained-attention reaction time; working memory; and mental arithmetic.
It is estimated that almost 20% of the accidents that happen on the road in the UK are due to sleep related incidents and are more likely to result in fatality or serious injury. (THINK!, 2017). 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).
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). If you want to read more about other factors which can impact our bone health, click here.
Sleep can affect bone health and normal growth in children and teens
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.
Our energy balance (which impacts our risk of obesity), is also impacted by our circadian rhythms, which is our 24-hour cycle, as well as our sleep-wake balance (Morselli et al., 2012). 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.
In addition to the risk of overweight and obesity, it has been suggested that our sleeping habits and the duration or restriction of sleep that can occur, are associated with risk of diabetes (Grandner et al., 2016). This is due to our impaired ability to tolerate carbohydrates and impaired glucose tolerance (Copinschi, 2005).
In those who have type 2 diabetes, those that work night shifts and are therefore not in the correct circadian rhythm, had a poorer glycaemic control than those who were working day shifts and those who were unemployed (Manodpitipong et al., 2017). In those with type 2 diabetes, those who had poorer sleep quality were found to have worse glycaemic control (Zhu et al., 2017). This shows that the disruption to our circadian rhythm can carry a whole host of impairments.
It has been found in obese adolescents (mean age 14.4 years old) that when they either had impaired sleep, or an excessive amount of sleep, it led to both short-term and long-term hyperglycaemia (high blood glucose levels) (Koren et al., 2011).
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 of 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).
It is thought that lack of sleep can lead to an increase in our blood pressure, causing hypertension (high blood pressure). It has been seen that even in those with hypertension and prehypertension, that even half a night’s sleep loss has been found to raise blood pressure (Mullington et al., 2009).
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).
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. If you want to find out more about how many hours the NHS recommend for sleep for other ages, click here.
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. If you want any further information on how to ensure that you get a restful night’s sleep, we have a blog available here.
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?
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Daisy is a Registered Associate Nutritionist with a Master's Degree in Public Health Nutrition, which is 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 and is currently studying for a PgDip in Eating Disorders and Clinical Nutrition.
Daisy has worked for an NHS funded project, the Diabetes Prevention Programme; and shadowed a nutritionist in Harley Street.
Daisy is Lucy's sister and is the Lucy Bee voice on all aspects of nutrition and its effect on the body.