Benefits of quality sleep Why sleep is important
We spend a third of our life asleep because sleep is vital to all of us – but doctors and researchers still don’t know the actual purpose of sleep. Sleep affects how we look, feel and perform. A good night’s sleep enables us to fully function and remain awake during the day: studies have shown a direct link between the amount and quality of sleep and our abilities the next day. During sleep our body repairs muscles, consolidates memories, and releases hormones needed for our health. Disruption to sleep, especially ongoing problems, affects our quality of life and can have a bad effect on our health and general well-being.
How do we go to sleep?
All of us have an internal 24-hour clock, the circadian rhythm, tells us to sleep when it’s dark and wake when it’s light. It is controlled by the amount of light to, which means artificial light, shift work, inter-continental travel can affect it. For most of us the circadian rhythm makes us most sleepy around 2:00-4:00 am and in the afternoon between 1:00-3:00 pm.
How melatonin helps regulate our sleep-wake cycle
Melatonin is a hormone naturally produced by the body. Hormones are ‘chemical messengers’ that have specific function within the body and the role of melatonin is very important in regulating sleep. Melatonin’s main function is to maintain the body’s natural time clock – also known as the circadian rhythm or body clock.
Melatonin production is affected by light; rising levels of melatonin as night falls tell your body that it is dark and time to sleep.
As we age, our ability to produce melatonin naturally decreases. It is this decrease over time which can causes sleep problems and insomnia, the elderly are particularly vulnerable.
What happens when we sleep?
We go through several sleep cycles a night when we sleep. Each lasts 90-110 minutes and include the so-called REM (rapid eye movement) and non-REM (NREM) sleep. The non-REM
sleep accounts for 3/4 of all sleep. We may wake up for 1-2 minutes during the night but most of us aren't aware of this and forget by the morning.
NREM has four stages, with stages 1 and 2 known as ‘light sleep’ and 3 and 4 as ‘deep’.
Stage one: light sleep when we're half awake and half asleep. Our muscle activity slows down and we may twitch a bit. We can still be woken up quite easily.
Stage two: true sleep occurs within ten minutes of light sleep and lasts about 20 minutes. Our breathing and heart rate are regular and body temperature drops. Stage three: deep sleep, which is the phase which rests and restores our body and mind. Our blood pressure drops, breathing becomes slower and our muscles relax.
Stage four: more deep sleep, there is rhythmic breathing and little movement of our muscles. It is very difficult to wake when in deep sleep and if we are woken we are likely to be very confused. In this stage, we may talk or even sleep walk. During this stage our body repairs itself, our energy is restored and hormones regulating growth and appetite, are released.
Stage five: this is REM sleep and usually begins approximately 90 minutes after the beginning of sleep. The length of REM sleep increases with each successive sleep cycle and is essential for helping us remain alert during the day. The first REM period usually begins about 70 to 90 minutes after we fall asleep. During it our brains are very active and our eyes dart around (hence the name), our breathing rate and blood pressure rise. But our bodies are not active and this is when we dream. REM sleep recurs about every 90 minutes, getting longer later in the night. Studies show that REM sleep is essential to us for daytime alertness. How much sleep do we need?
This varies depending on the person and their age. Children and teenagers need more than adults because their bodies are still growing; babies may need as much as 19 hours during a 24-hour period. Most adults will need between six and eight hours a night to function at their best the next day but there are many adults who manage well on just four hours sleep a night. There are also some who need much more sleep than 8 hours. However, often, as we get older, our routine changes and we might have more opportunities to cat nap during the day. This can change our circadian clock.
As we age we need less sleep; many elderly people need only six hours a night and can find that they wake earlier in the morning. This can be due to physiological changes which occur naturally with age.
You should plan your day to enable you to get the sleep you need and to wake up in the morning refreshed and ready for the day ahead. Establishing a regular schedule for going to bed and getting up will promote sleep by getting you in harmony with your circadian clock, so that you get enough sleep to maintain wakefulness during the day.
What is good quality sleep?
Falling asleep quickly when you feel ready for sleep, waking up when you want to, feeling recharged and ready for the day, staying on the ball until you next want to sleep the following evening
are all indicators of a good night’s sleep. Good quality sleep is associated with going through the sleep cycle several times a night and spending enough time in stages three and four of NREM and stage five of
REM sleep .
References Zammit GK, Weiner J, Damato N, et al . Quality of life in people with insomnia.
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Sleep Med Rev 2001; 5(6): 423–445 Pilcher JJ, Ginter DR, Sadowsky B.
Sleep quality versus sleep quantity: relationship between sleep and measures of health, well-being and sleepiness in college students. J Psychosom Res 1997; 42(6): 583–596 Royal College of Psychiatrists Sleeping Well, 2005. What happens when you sleep? National Sleep Foundation. Kandel ER, Schwartz JH, Jessell TM. Principles of neural science.
© The McGraw-Hill Companies Inc, 2000. [TM Page 2.18]
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