We spend approximately one third of our lives sleeping. Sleep occurs in all living organisms and is a vital part of our functioning.
There are a number of factors that both promote and aid our ability to fall asleep. One of these factors is timing of sleep.
Sleep often occurs at night due to the following factors:
A chemical builds up in our brain making us sleepy, this switches on the sleep process. This chemical is blocked by caffeine which is why coffee and tea keep us awake.
The eye senses light which then resets our internal body clock, sending a message to our sleep centre to switch on the sleep process. Our internal body clocks are genetically programmed to make us short sleepers or long sleepers.
When we first fall asleep the body starts to relax and the breathing becomes slower and deeper. Occasionally we can feel “hypnogogic jerks”, these are sudden jerks that can cause awakenings, though thy rarely prevent us from falling asleep.
Sleep occurs in cycles; light sleep, deep sleep then ‘dream state’ or REM sleep. Each cycle lasts approximately 90 mins. We have three to four cycles in an average night.
During deep sleep our body relaxes, and the breathing becomes slow and deep, the brain waves frequency also slows. When we are awoken from this state, we can feel very disorientated for a few minutes.
In dream state sleep, we have very fast mixed frequency brain waves which are of a similar pattern to our waking state. Our bodies are completely relaxed and unable to move much. When we are awoken from this state, we may remember our dreams and, if waking suddenly, we may feel as if we cannot move. The breathing and heart rate are often very erratic during this state.
We need, on average, 7-8 hours’ sleep to function well.
If sleep is disturbed, we can compensate for a short time, but the processes for coping will eventually wear out and we will start to feel tired or sleepy during the day. Memory function decreases, resulting in more forgetfulness.
Disorders of sleep occur when any stage of the natural sleep process is interrupted, either suddenly or over a longer time. Sleep disorders often result in two things; loss of deep sleep and the total amount of sleep had, regardless of time spent in bed. This is termed sleep efficiency and if reduced can cause long-term sleepiness, loss of concentration and decreased cognitive function.
Sleep disturbance can also be caused by conditions which cause multiple short awakenings during sleep called arousals. These often prevent the body from staying asleep.
SNORING AND UPPER AIRWAYS RESISTANCE SYNDROME
Snoring is the sound produced by the structures in the mouth and throat vibrating whilst we are breathing during sleep. Snoring can cause sleep disturbance to the individual, but often causes social problems and sleep disturbance to others around as well.
Breathing in sleep may restrict the flow of air from the nose into the lungs. If airflow restriction is severe, it can cause a sleep disturbance known as Upper Airways Resistance Syndrome.
Upper Airways Resistance Syndrome may be caused by nasal stuffiness and congestion, as well as reduction of the total space in the throat for air to flow into the lungs.
Sleep Apnoea is caused by the airway space in the mouth and throat reducing to the point at which there is no flow of air into the lungs. Each apnoea must last at least 10 seconds to be considered significant. The reduction of airflow to 50% of normal is called a hypopnoea, this must also last at least 10 seconds and cause a drop-in blood oxygen levels.
Sleep apnoea may be categorised as:
Mild 5-15 episodes per hour
Moderate 15-30 episodes per hour
Severe over 30 episodes per hour.
Sleep apnoea only occurs during sleep, it develops slowly and affects sleep quality by causing arousals in sleep i.e. broken sleep. Sleep apnoea has many associations with heart disease, strokes, diabetes and dementia.
However, most patients complain of sleepiness during the daytime long before the harmful effects of sleep apnoea occur.
Sleep apnoea may also be associated with an increase in blood pressure, due to the stimulation of the body during the night to stay in a light sleep/waking state.
Obesity can cause sleep apnoea; this can be resolved with weight loss.
RESTLESS LEG SYNDROME
Restless Leg Syndrome is a condition which occurs more commonly in the over 50s. Symptoms involve unpleasant sensations in the legs when sitting at rest, which may improve upon walking and movement. Some may experience the sensation of insects crawling up the legs and find this symptom worsens in the evening. Restless leg syndrome can disrupt sleep due to repetitive leg twitches during the night. Restless leg syndrome often requires treatment.
PERIODIC LIMB MOVEMENTS DISORDER
A large proportion of the population experience repetitive limb movements during the night and often these are of no consequence. If you have daytime sleepiness associated with periodic limb movements at night these may be causing awakenings and disrupting sleep.
Unusual behaviours during the night, for example sleep walking and sleep talking, are termed Parasomnias. These are not harmful and rarely need treatment, they are purely self-limiting. Very rarely other sleep disorders may be noticed such as; groaning at night (Catethrenia), acting out dreams (REM Behaviour Disorder) or recurrent night terrors and nightmares. Parasomnias require specialist sleep studies to diagnose these.
Narcolepsy is a rare condition which occurs when the central process for wakefulness is damaged. Profound sleepiness occurs during the daytime despite adequate sleep at night. There may be disturbed sleep at night as well as sleep attacks during the daytime.
Narcolepsy may be an autoimmune condition which may take more than 20 years to diagnose from the original episode. Narcolepsy has also been known to occur following infections such as influenza, encephalitis and glandular fever. Very rarely narcolepsy can occur after a significant head injury.
Narcolepsy sufferers find daytime naps are often needed in order to function.
A very rare form of Narcolepsy with Cataplexy is known to occur if the person finds that they collapse or suffer weakness when experiencing emotional states such as laughing and crying.
Insomnia occurs if patients cannot fall asleep or stay asleep, currently incidence of insomnia in the general population is up to 40%. Chronic insomnia may be diagnosed if sleep is disturbed three night a week or more, for three months or longer.
Insomnia may be caused by many different factors, each needing to be explored through careful detailed discussion.
Insomnia has been linked with worsening health of the sufferer later in life. A number of scientific studies have linked untreated insomnia with the following:
Failure of relationships
Mental health problems
Accidents at work
Reduction in immune system functioning.
Reduced fertility and or libido
CIRCADIAN RHYTHM DISORDERS
Circadian Rhythm Disorders are disruptions in a person’s Circadian Rhythm – our internal body clock. Our bodies contain genes colloquially referred to as Clock Genes. Clock Genes control most hormonal and behavioural body rhythms, such as when we feel the most sleepy or most alert. In fact, most of the life on earth, such as plants and animals, are controlled by clock genes.
These genes cycle over 24 hours. Timing is closely aligned to the earth’s day and night cycle by a master clock called the Suprachiasmatic nucleus.
The master clock may work out of synchronisation in cases such as when a person travels across more than three time zones. This master clock often alters in puberty, resulting in teenagers sleeping later in the night as well as awakening later.
Disorders of the master clock often lead to extreme variation in timings of sleep (i.e. the sleep pattern).
Delayed sleep phase syndrome is a Circadian Rhythm Disorder which results in later bedtimes and, consequently, later waking times.
Advanced Sleep Phase Syndrome occurs when the bedtime and rise time are much earlier than normal.
Free running sleep rhythm occurs due to loss of the entrainment and therefore resetting of the master clock. The sleep onset at bedtime is advanced or occurs later each day. People who experience this may eventually reverse their sleep timing so that they are awake all night and asleep all day.
These Circadian Rhythm Disorders are common and respond well to treatment.