The Importance of Sleep

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 ‘Each night, when I go to sleep, I die. And the next morning, when I wake up, I’m reborn.’

Mahatma Gandhi

What is sleep?

Sleep is one of the most important, essential and worthwhile things that humans do. Sleep-time is when our bodies and minds are allowed to recharge, leaving today behind and getting ready for tomorrow. When we sleep well, we go into a deep state of rest in which the body restores itself, building healthy tissues, blood cells and muscle. 

Good sleep also helps regulate weight, blood pressure, glucose levels and hormone production, memory formation and mental health. The mind recuperates from daily activities and processes the experiences of the past hours, helping us with problem-solving and memory creation. 

Conversely, inadequate sleep can result in various disorders, such as diabetes, hypertension, psychiatric issues and obesity, among others. Without adequate sleep, we feel tired and irritable, and have lowered cognitive abilities and memory loss. We are less productive which leads to a lack of discipline and focus in our daily activities. We dream when we sleep. Dream-time is crucial for consolidating our memories, moving them from our short to long-term memory bank, and aiding us in sifting through experiences and problem solving while we are asleep.

The four stages of the sleep cycle

Once we are asleep, our bodies enter a four-stage sleep cycle. The four stages repeat throughout the night until we wake up again. Typically, each cycle lasts between 90 and 120 minutes.

The first three of the sleep stages are known as non-rapid eye movement (NREM) sleep (NREM sleep makes up 75% to 80% of each cycle. People may also wake up briefly during the night but not remember this the following day. These episodes are known as ‘W’ stages). The fourth stage is known as REM (rapid eye movement).

  • Stage 1 NREM: This first stage marks the transition between wakefulness and sleep. It consists of light sleep where the muscles relax and the heart rate, breathing, and eye movements begin to slow down. Likewise, our brain waves, which are more active when we are awake, slow. This first stage usually lasts several minutes.
  • Stage 2 NREM: This second stage is characterised by deeper sleep. Heart and breathing rates continue slowing down and muscles become more relaxed. Eye movements cease during this stage and body temperature decreases. Apart from brief moments of higher frequency electrical activity, brain waves also remain slow. This stage is typically the longest of the four sleep stages.
  • Stage 3 NREM: In this third stage, the heartbeat, breathing and brain wave activity reach their lowest levels and muscles become as relaxed as possible. This period of deep rest and relaxation plays an important role in helping us feel refreshed and alert the next day. Stage 3 is long at first but decreases in duration throughout the night.
  • Stage 4 REM: The first REM stage occurs about 90 minutes after we fall asleep. During REM sleep, the eyes move rapidly back and forth under the eyelids. Breathing rate, heart rate and blood pressure begin to increase. Dreaming typically occurs during REM sleep. At this point, the arms and legs become paralysed. This is to prevent us from physically acting out our dreams. Each REM sleep cycle gets longer as the night progresses. Many studies have linked REM sleep to memory and the process in which recently learned experiences are converted into long-term memories. As we age, the duration of the REM stage decreases, causing us to spend more time in NREM stages.

How much sleep does a person need each night?

‘Three meals plus bedtime make four sure blessings each day.’

– Mason Cooley

Getting the correct amount of sleep is vital for optimum mind and body functioning. One of the biggest myths about sleep is that a few hours of proper sleep at night is enough to function at optimum level during the day. 

Studies indicate that people who get less than the recommended seven hours of sleep per night have an increased risk for many health problems. Over time, inadequate sleep and fragmented sleep may have negative effects on our brain, our mental ability and our physical health.

Research shows that the optimum sleeping time for adults is between seven and nine hours nightly. Children and teenagers need significantly more sleep, especially when they are under than five years of age. 

The optimum amount of sleep for each person depends to a large extent on what age we are, reflecting that sleep-time is not written in stone and changes throughout our life. 

The US National Sleep Foundation recommends the following daily sleep for different age groups.

Age Group Age Range Recommended Amount of Sleep per Day
Newborn 0-3 months 14-17 hours
Infant 4-11 months 12-15 hours
Toddler 1-2 years 11-14 hours
Preschool 3-5 years 10-13 hours
School-age 6-13 years 9-11 hours
Teen 14-17 years 8-10 hours
Young Adult 18-25 years 7-9 hours
Adult 26-64 years 7-9 hours
Older Adult 65 years or older 7-8 hours

Circadian rhythm and light

We all have an internal body clock that regulates our sleep cycle. This clock controls when we feel tired and ready to go to sleep. It also controls when we are refreshed and ready to start our day afresh. The circadian rhythm is the 24-hour cycle on which this internal clock operates.

A hugely influential external factor on our circadian rhythm is light, both natural and artificial. A cluster of cells in the brain’s hypothalamus processes signals when the eyes are exposed to natural or artificial light. These signals help the brain determine whether it is day or night.

As natural light disappears in the evening, the body releases melatonin, a hormone that induces drowsiness. When the sun rises in the morning, the body releases the hormone cortisol, which promotes energy and alertness.

When we are exposed to too much light, the production of melatonin is reduced. Our circadian rhythm is tricked into thinking it is still daytime and that we should remain awake.

We live in a world lit by artificial light, making it increasingly difficult for the body to maintain a healthy sleep-wake cycle. The greatest culprit is blue light – the light that comes from smartphones, televisions, tablets and computers. Studies show that over-exposure to blue light leads to reduced melatonin levels and misaligned circadian rhythms. 

Studies also show that people who live in areas with more outdoor night-time lighting are more likely to report having issues with sleep and feeling tired during the day. By 2050, 70% of the world’s population will be living in urban areas, potentially not getting enough natural daylight or natural nightlight.

Know your chronotype

While getting the correct number of hours’ sleep is hugely important, going to sleep at the right time for you is also very important. We all have a chronotype, which is the natural inclination of the body to sleep and wake at a certain time. As well as regulating sleeping and waking times, our chronotype influences our appetite, our ability to exercise and our core body temperature.

We are all familiar with the terms ‘early bird’ and ‘night owl’ and these are useful shorthand for knowing which chronotype you have.

Most young children have an early chronotype. This changes when they enter teenage years and begin to sleep later in the day, often finding it difficult to wake up for school, or before noon. From young adulthood – around the age of twenty – starts getting earlier again. By middle age, most adults are best served by going to bed at 11pm and waking up between 7am and 8am. When we are in older age, those hours get earlier again.

While our chronotype changes naturally during the course of our life, scientists consider it almost impossible to change your chronotype on purpose to suit your work or social lifestyle. Many people’s chronotype is at odds with their work and life demands, leading to what is termed ‘social jetlag’.

Night owls (those who prefer naturally to get up later and go to bed later) are particularly exposed to suffering from social jetlag. If work or school demands an early start, they may suffer from ongoing tiredness. Likewise, early risers don’t do so well if they are obliged to be awake late into the evening or night.

The mismatch between our personal chronotype and work/school times can have an ongoing adverse effect on how we perform and feel. The ideal would be for workplaces and schools to recognise, at the very least, the fact that people have different chronotypes and can’t always be at peak performance. The effects of sleep deprivation on people can, over a long period of time, be detrimental to overall health, performance and wellbeing.

While we usually talk of two chronotypes, the fact is that chronotypes exist on a spectrum with the majority of people falling somewhere in the middle. Sleep researchers refer to this group as ‘hummingbirds’. 

You probably already have a good idea of your chronotype and know whether you like to wake up early or later naturally. To get a better insight, questionnaires have been developed by scientists that help people identify their chronotype. It can be very useful to know yours as a basis for developing good sleep habits and, if possible, adjust your schedule to suit your chrontype. 

The Morning Evening Questionnaire (MEQ) and the Munich ChronoType Questionnaire (MCTQ) are both available online. A popular quiz, by Dr Michael Breus, outlines four types of chronotypes, based on sleep-wake patterns seen in animals. If you complete this questionnaire, you will find out whether you are more of a bear, wolf, lion, or dolphin.

  • Lion (early bird): Lion chronotypes wake up early and are most productive in the morning. They may have difficulty following through with an evening social schedule.
  • Bear: Bear chronotypes account for approximately 55% of the population. Bears tend to follow the sun. They do well with traditional work hours and have no problem maintaining an evening social life.
  • Wolf (night owl): Wolf chronotypes make up approximately 15% of the population and follow the classic night owl hours of late to bed and late to rise. 
  • Dolphin: Dolphin chronotypes (of the human variety) are considered insomniacs, mirroring the ability of real dolphins to stay alert even while sleeping.

What are the common factors that stop us from getting a good night’s sleep?

Outside of personal biological and genetic factors, modern life today is generally not conducive to good sleep habits. Work schedules, day-to-day stressors, a disruptive bedroom environment, and medical conditions can all prevent us from receiving enough sleep. While a healthy diet and positive lifestyle habits can help ensure a good night’s sleep, for some, chronic lack of sleep may be the first sign of a sleep disorder.

Factors that negatively affect good sleep:

  • Light pollution: Increased exposure to artificial light is disrupting our natural circadian rhythm. This brain’s hypothalamus processes signals when the eyes are exposed to natural or artificial light. These signals help the brain determine whether it is day or night. In a world of near-constant light, it has become increasingly difficult for our brain to know when it is time to sleep.
  • Noise pollution: Studies show that, globally, there are thousands of deaths annually due to noise pollution, and millions of cases of hypertension due to noise.
  • Technology: Advancement in technology, many of them so helpful, also mean that the lines between on and off have become blurred. This affects our ability to switch off and has made it increasingly difficult to draw the line between work and non-working time.
  • Online life: Between reading, gaming, consuming news, watching programmes, many people of all ages find it difficult to contain the time spent in front of their screens. Over 80% of adults use their phones in bed. The blue light from screens plays havoc with our circadian rhythm and we are not getting any natural winding-down time before attempting to go to sleep.
  • Stress and anxiety: Stress is one of the biggest modern-day sleep disruptors. When we go to bed stressed, it becomes very difficult to fall asleep. We become anxious about not being able to fall asleep, leading to a vicious circle and depleted sleep. 
  • Partners: Studies show that 25% of people find it difficult to sleep because of the presence of a partner with a different sleep-environment need. This includes different body heats, the need for more/less bedding, wanting the light on/off, and snoring.
  • Societal acceptance, and even glorification of, shorter sleeping times: For decades, western society, in particular, has applauded those who prioritise a long work day over all else, including proper, daily sleep. We have put so-called ‘workaholics’ on pedestals, admiring and envying the fact that they sleep so little. This, we have told ourselves, is what real success looks like. The (mostly) men at the head of some of the world’s best-known and biggest companies boast about their four and five-hour nightly sleep. In this way, they have become cheerleaders for today’s sleep deprivation epidemic. 
  • Snoring and sleep apnoea: Most people snore as they age and it impacts how tired we are the following day.
  • Revenge bedtime procrastination: This is the decision we make to sacrifice sleep (even though we may be tired and want to go to bed) for leisure time. It is driven by a daily schedule that is lacking in free time. We resent that we don’t have time for ourselves and so steal from our sleep time to satisfy the need to have some ‘me-time’.

The effects of chronic and long-term sleep deprivation

‘Sleep is not like the bank, you can’t accumulate a debt and then pay it off at a later point in time’

– Matthew Walker

Good sleep is as important for human health and wellbeing as food, water and air. Despite most adults agreeing on this, one third of us are not getting enough sleep. This is a global phenomenon right across almost all age groups. So serious is the knock-on effect of sleep deprivation that it has been called an epidemic.

Studies show that sleep deprivation makes people vulnerable to loss of attention, impaired cognition, mood shifts, and delayed reaction times.

A recent study shows that 62% of adults feel they are not getting enough sleep, with most registering an average of 6.8 hour on weeknights and 7.8 hours on weekend nights. The recent pandemic has only added to sleep problems, with online searches relating to insomnia up by over 50%. 

The number of people with actual sleep disorders is also increasing. These include insomnia, sleep apnoea, narcolepsy, and restless leg syndrome.

It has been suggested that, over time, people can develop a type of tolerance to ongoing sleep deprivation, to the point where they don’t know that they are struggling with lack of sleep. This is because sleep deprivation feels normal to them.

We all know what it’s like to have a bad night’s sleep. We feel groggy, irritable, unfocused and tired the next day, and most likely perform badly at work. And that’s just after one night of insufficient sleep.

Not getting enough sleep over the longer term increases our chances of reporting with certain chronic health conditions, including depression, high blood pressure, heart disease, stroke, Type 2 diabetes, poor mental health, and obesity. It also increases our likelihood of dying earlier.

In addition to the direct effect on ourselves and our ability to perform our work, there are wider, societal effects of insufficient sleep. These include what is known as ‘drowsy’ or ‘tired’ driving. Tiredness lessens our cognitive abilities and decreases our ability to drive safely.

It is estimated that driver fatigue is a contributory factor in as many as one in five fatal crashes in Ireland every year. In Ireland, 28% of motorists in Ireland say they have fallen asleep or nodded off, even if only for a moment when driving.

The effect of driving while tired is similar to that of driving when under the influence of alcohol.

Counting the economic cost of sleep deprivation

Lack of sleep makes people less productive and this is costing employers and governments lots of money. Sleep-deprived people turn up to work alright, they just don’t perform as well as they would if they’d had a good night’s sleep. 

Studies that take into account the macroeconomic cost of sleep deprivation estimate that the cost to the US economy is $411 billion annually. Sleep deprivation in other developed nations, such as the UK, Japan, and Germany, is estimated to cost between 1-3% of GDP annually. 

Addressing the public health crisis of sleep deprivation

For much too long, the core importance of healthy sleep to humans has been sidelined. But the tide is finally turning as people come to realise that the cost – personal, societal and economic – is too high. 

The starting point is governments investing in public health campaigns to raise national awareness on the vital importance of healthy and sufficient sleep. Health professionals will also need to lead the way in teaching their patients the importance of proper sleep routines. 

Changing societal and personal attitudes towards sleep and its vital role in our lives is key to turning the tide on the sleep deprivation epidemic and its costs.

Establishing healthy sleep habits

How we sleep changes over the duration of our lifetime. It is not written in stone. This is great news for those of us who are not getting a good night’s sleep – we can change our habits and, consequently, change how we sleep. We can, essentially, rewrite our sleep script by implementing positive lifestyle and sleep habits in order to get required amount of sleep-time that we need. 

Daily actions that aid sleep 

  • Soak up the sky first and last thing each day. Get exposure to morning light as this resets your circadian rhythm and helps the body to produce the hormones that give you energy (cortisol), and make you sleepy (melatonin) later in the day, indicating that is time to go to bed.
  • Exercise during the day, preferably outdoors, as this will help you wind down in the evening.
  • If you need to take a nap during the day, try to do so before 3pm as napping any time after than can interfere with the night’s sleep. Ten to 20 minutes is the optimum time for a nap, which should be taken in a quiet, calm environment that has a comfortable temperature.
  • Make sure you keep hydrated throughout the day.

What to eat and drink

  • Be careful about what you eat in the evening. Although it’s believed that caffeine, chocolate, certain meats and alcoholic drink stimulate brain alertness, their effects are not the same for everyone. It’s important that you work out what food and drink keep you from having a full night’s sleep, and avoid consuming them in the evening.
  • Avoid salty, spicy and sugary food before bedtime.
  • Avoid alcohol in the hours before bedtime (using alcohol as a sedative decreases the quality of our sleep by 24% and alcohol will wake you up in the second part of the night.

Prime your bedroom for sleep

  • Maintain a comfortable temperature of 17-18˚ Celsius in your bedroom.
  • Keep lights dim as this triggers the production of melatonin which aids sleep.
  • Invest in a good mattress that suits your body, and comfortable pillows, sheets and duvet that meet your sleep preferences and body type.
  • Do not have screens or electronic devices in your bedroom.
  • Bedroom space is for sleep and intimacy, don’t clog it with anything else.
  • If you wake in the middle of the night, wait for approximately 30 minutes to see if you will fall back to sleep. If you don’t, get out of bed and move to another room, turn on a dim light and read something relaxing. Only return to bed when you are sleepy as you don’t want your bedroom to become associated with sleeplessness.

Watch your self-talk around sleep

  • If you keep telling yourself that you can’t sleep, then chances are you won’t have a good night’s sleep. Our perception of how well we sleep changes the quality of our sleep and how well we actually sleep.
  • Stop sabotaging your chances of having a good night’s sleep by being careful with negative self-talk about how you expect to sleep.
  • Focus on how you will feel after getting a good night’s sleep.
  • Reward yourself when you sleep well. The brain responds to and registers rewards and this can help in the formation of good sleep habits.
  • Stop thinking that you won’t get a good night’s sleep.
  • While sleeping pills and sedatives may be useful in the short-term, they are not advisable in the long-term. 

Get ready for sleep time

  • Establish a regular going-to-bed and getting-up time and stick to it every day, even on the weekends.
  • Start to get ready for bed an hour before you go to sleep. Turn down the lights, turn off technology, listen to calming music or read a soothing book. If you must watch TV or a streaming service out of habit or as a sleep aid, try and do this about two hours before you go to bed; set a time limit for watching and stick to it; don’t have the volume too high; avoid action-packed, violent programmes.
  • Don’t do dynamic exercise earlier in the hour or so just before bedtime as the stimulating hormones and neurotransmitters released by vigorous exercise make it difficult to get into deep-sleep mode.
  • Avoid screens or, at best, use blue light blocking software for devices. 
  • Stop thinking about things that you can’t do anything about.
  • Avoid stressing over what happened during the day or what is ahead of you tomorrow. Try writing down your concerns in a notebook a few hours before bedtime so you can ‘park’ these concerns until the following morning.


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