Feature – What is Sleep?
Sleep is vital to life.
It can be defined as- ‘being in a state of rest when your eyes are closed, your body inactive and your mind is unconscious.’
Physiologically sleep provides a natural restorative and regenerative process for our bodies. Many of our major organs continue to work actively and muscle growth, tissue repair, protein synthesis and the release of the growth hormone occur while we sleep. Sleep also helps our immune system to recover. These vital tasks carried out during sleep help to maintain good health and enable our minds and bodies to function normally during the day.
An internal body clock regulates the timing for sleep by programming us to sleep during the night and to be active during the day. Light causes the biological clock to synchronise to the 24 hour cycle of day and night. Disruptions of this body clock can make us sleepy when it is important that we stay awake and remain alert.
WHAT HAPPENS WHEN WE SLEEP
Sleep occurs in recurring cycles of 90 to 120 minutes length and is divided into two categories – Non REM (Rapid Eye Movement) sleep and REM sleep
Non REM sleep is divided into 3 stages which are determined by the pattern of brain activity.
Stage One is light sleep or the transition from wakefulness to deeper sleep. Some people may not think they are asleep at this stage. Muscle activity and brain waves slow down and some twitching may occur during this time. This stage usually lasts for about 10 minutes.
Stage Two is a true sleep state. Heart rate and breathing rate begin to slow down and response to external stimuli such as light and noise gets less as the brain shuts down.
Stage Three is known as deep sleep. Breathing and heart rate are at their lowest during this time and muscle activity is limited.
REM Rapid Eye Movement) sleep (also known as dreaming sleep). When we are dreaming our eyes move backwards and forwards under the closed eyelids. During REM sleep heart rate increases, body processes speed up and breathing is irregular. If we are woken up during this cycle we will usually recall our dreams and be less confused and more ‘with it’ as the brain is very active.
Fortunately our bodies are effectively paralysed during REM sleep to prevent us from acting out our dreams which could in some situations have severe consequences. This stage usually begins 70-90 minutes after we fall asleep and usually lasts for 20-30 minutes.
Generally we have 3-5 episodes of REM sleep each night.
WHAT HAPPENS IF WE DON’T SLEEP?
Lack of sleep has serious effects on our brain and our ability to function normally during the day. It can impact on our performance, concentration and reaction times, lead to depression and increase the risk of accidents whilst driving or in the workplace
If we continually get less sleep than we need we can develop a sleep debt which may have serious consequences.
In the long term sleep deprivation can lead to health problems such as obesity, diabetes and increased risk of heart disease and hypertension.
One very common, but under-diagnosed sleep disorder which causes sleep deprivation is Obstructive Sleep Apnoea (OSA). Sufferers of this condition have disruptions in their sleep cycle due obstruction of the upper airway which causes complete or partial cessation of breathing during sleep. The signs of this condition are loud snoring and excessive daytime sleepiness
Obstructions occur during sleep for two primary reasons: lack of muscle tone and gravity. Excess tissue and anatomic abnormalities in the upper airway can also compound these factors. During sleep, especially in REM (dream) sleep, our bodies relax and muscle tissue like the tongue and soft palate lose tone. As we tend to sleep lying down, gravity pulls these tissues towards the back of the throat causing the airway to narrow and then to close off completely.
Each obstruction means that air is unable to enter or leave the lungs so the body is deprived of oxygen and is forced to retain carbon dioxide that would normally be exhaled. As a result blood gases become unbalanced and the body is subjected to a ‘toxic’ environment. When the body sets off ‘alarms’ that it needs more oxygen, the brain arouses the person, they come up to the lighter stages of sleep and the airway reopens. These obstructions and arousals can occur hundreds of times during the night.
These brief arousals diminish the quality of sleep and cause sleep deprivation which can lead to depression, irritability, daytime sleepiness, and an inability to concentrate during the day.
For more information visit www.osauk.org
Some people have difficulty in falling asleep or staying asleep. This is known as insomnia. Research has shown that up to 2/3rds of the population can suffer with this.
Insomnia can be caused by many things such as anxiety, stress, jet lag, irregular work shift patterns, poor sleep hygiene, other underlying medical conditions and even some medications, Short term insomnia lasts for 1- 4 weeks If it carries on for longer than 4 weeks it is known as long term or persistent insomnia
Insomnia can have the same consequences as those described for sleep apnoea
If insomnia persists it should be discussed with your GP.
Individuals vary in their need for sleep but the National Institute for Health suggests that the average adult needs 7-9 hours sleep each night. However every individual is different, some people need less sleep and are still able to function quite normally while others need more. As we get older we tend to need less sleep.
Many of us have poor sleep habits. Sleep hygiene suggests measures that we can follow to help us to enjoy quality sleep.
- Avoid drinks such as coffee, tea and Coca Cola which contain caffeine before bedtime. These are stimulants and can keep you awake
- Limit alcohol consumption as while this may help you to get to sleep it can disrupt sleep in the early hours and can cause you to wake up later on in the night.
- Avoid strenuous exercise for at least two hours before you go to bed.
- Do not have a large meal late in the evening and avoid foods that can cause indigestion.
- Do not have too much fluid close to bedtime so that you will not wake up needing to go to the bathroom.
- Keep a regular bedtime and get up at the same time every day.
- Establish a relaxing bedtime routine. Have a bath or read for a short time before you settle down to sleep
- Ensure that your bedroom is conducive to sleep – have a quiet, cool comfortable environment and keep pets out of the bedroom.
- Do not nap in the evening
- Try not to dwell on problems when you go to bed.
The amount of sleep we get and the quality of it is important in maintaining overall good health and a feeling of well being. We all want to be able to wake up feeling refreshed and better able to face the day ahead.