Disease Info - Sleep Studies
What is Sleep?
Sleep is a behavioural state characterised by little physical activity and almost no awareness of the outside world. Sleep is an active, highly organised sequence of events and physiological conditions and is made up of two distinct states: (1) Non Rapid Eye Movement Sleep (NREM); and (2) Rapid Eye Movement Sleep (REM).
The Sleep pattern
NREM sleep is divided into 4 stages. Stages 1 and 2 are known as "light sleep", and stages 3 and 4 are known as "deep sleep". Normal adults will enter sleep via NREM light sleep and deep sleep will predominate the first third of the night. REM sleep is also called "dream sleep" and this stage predominates the last third of the night. Normal adults cycle through NREM and REM sleep approximately every 90 minutes. It is this typical sleep stage distribution that defines healthy sleep in an adult.
The Circadian Rhythm
The timing and control over wakefulness and seep depends on our bodies' biological clock or "Circadian rhythm".
This clock is sensitive to light and has evolved to the 24 hour light/dark cycle of our world. In humans sleep is physiologically programmed to come each night. The timing of sleep and wake is controlled by our exposure to natural light and dark cycles of the earth. It takes the body several days to change to a different light-dark schedule. Individuals who sleep in an environment free from time cues follow a shorter rhythm for the onset of sleep and length of sleep.
Sleep and Ageing
One of the factors affecting sleep is age. The sleep of an infant is very different to that of a healthy middle aged adult described above. NREM sleep is not present at birth and evolves over the first 2-6 months of life. Deep sleep is then maximal in young children, decreasing by 40% by adolescence. By the age of 60 years, deep sleep diminishes dramatically and may no longer be present, however REM sleep as a percentage of total sleep is maintained in healthy old age. Arousals from sleep also increase with age. However, it is unclear whether this is a direct effect of age or because older people having more causes of sleep disturbance e.g. sleep disorders, pain.
Sleep loss or sleep deprivation can occur in an individual as result of
A sleep disorder,
Shift work; or
Apart from sleep loss causing daytime sleepiness, it also has an effect on the next "normal sleep cycle"; when sleep is next available. Deep sleep will usually dominate after a period of sleep deprivation. If partial sleep deprivation has occurred then rebound of the deprived sleep stage will occur when normal sleep resumes.
Sleep disorders can dramatically affect the normal sleep cycle. Common ones are:
Obstructive Sleep Apnoea (OSA) is a condition where the airway narrows during sleep causing the sufferer to stop breathing many times during the night. People with this disorder have a more fragmented sleep pattern with reduced deep sleep and REM sleep.
Narcolepsy is a disorder causing episodes of unpreventable sleep, which can occur frequently and at inappropriate times. These episodes are usually REM-based sleep. Sufferers of narcolepsy have a short delay to REM sleep. This abnormal sleep pattern can see components of REM sleep entering the wake state causing hallucinations, sleep paralysis and cataplexy.
Sleep and Alcohol
The occasional use of alcohol and chronic alcoholism has been linked to sleep disturbance. Initially, alcohol use leads to an increase in NREM deep sleep and can lead to reduced REM sleep with continued use. Following this, increased sleepiness, restless sleep and often vivid dreams during the second half of the night are experienced. With continued habitual use, alcohol continues to show a short lived sedative effect, followed by sleep continuity disturbance for several hours.
Sleep and Drugs/Medication
Drugs and prescription medication can also affect sleep. Caffeine is known to result in increased wakefulness and sleep fragmentation and reduce deep sleep. Illicit drugs such as cocaine and amphetamines increase the time it takes for you to fall asleep. They also result in a reduced total sleep time and break up of sleep architecture. Amphetamine use also reduces REM sleep and deep sleep. Sedatives and sleeping pills produce an increase in sleepiness. They also decrease REM sleep and increase "sleep spindle activity", which is a feature of light sleep. Long term use of sedatives may actually induce symptoms of insomnia as the person becomes dependant.
What is Sleep Apnoea?
"Apnoea" is a word used to describe complete absence of breathing for more than 10 seconds, which usually occurs during sleep. Apnoea can be:
Central - where no effort is made to breathe,
Obstructive - where no breathing occurs despite repeated efforts to suck air into the lungs against a blocked upper airway; or
Mixed - where there is a combination of effort to breathe and no effort to breathe.
The most dangerous is Obstructive Sleep Apnoea (OSA), which is characterised by repetitive pauses in breathing during sleep due to collapse of the upper airway, which is usually accompanied by a reduction in oxygen levels in the blood, and followed by an awakening to breathe.
How does Sleep Apnoea occur?
Obstruction of the upper airway occurs when the muscles of the upper airway (including the tongue and soft palate) become too relaxed, either narrowing significantly, or completely blocking the airway, and preventing breathing. This leads to snoring and breathing difficulties, and breathing often stops for more than 10 seconds.
The brain then reacts to stopping breathing, and alerts the body to wake up or move to a lighter level of sleep. In most cases, the sufferer will be unaware of this. However, as this can happen several hundred times during the night, it is enough to fragment sleep, causing the sufferer to feel sleepy and lethargic the next day.
What are the Risk Factors?
You are most likely to have, or to develop sleep apnoea, if you have any of the following symptoms:
If you experience loud snoring,
If you are overweight or have gained excessive weight - accumulation of fat on the sides of the upper airway causes it to become narrow and inclined to close when the muscles relax,
If you have high blood pressure,
If you have heart rhythm abnormalities, or
If you have some physical abnormality in the nose, throat, or other parts of the upper airway.
Additional Risk Factors
In addition to the factors listed above, other risk factors include:
Being male (although OSA is probably under-diagnosed in women) - this is because male hormones can cause structural changes in the upper airway,
Age - loss of muscle mass is a common consequence of the aging process;
Smoking and alcohol use; and
Genetics/Family history - Seep apnoea appears to run in some families, so it can affect both males and females of all ages, regardless of their body weight.
What are the Symptoms?
The symptoms of OSA result from disruption of the normal sleep architecture.
Warning signs may include:
Choking or gasping during sleep
Loud, repetitive snoring
Recurrent awakenings overnight
Excessive daytime sleepiness
Early Diagnosis is Crucial
Early recognition and treatment of sleep apnoea is critical because the frequent arousals and the inability to achieve or maintain the deeper stages of sleep can lead to:
fatigue and excessive daytime sleepiness,
much higher risk of motor vehicle accidents and Occupational Health & Safety breaches in the workplace,
decreased memory; and
increased risk for other medical conditions, including irregular heartbeat, high blood pressure, heart attack, and stroke.
If you are experiencing tiredness or sleepiness during the day, loud snoring or pauses in breathing during sleep or any other sleeping difficulties, please take the Epworth Sleepiness Scale test (overleaf) and discuss these problems with your doctor.
*Ref Young et .al. N Eng J Med 1993
Snoring is noisy breathing through the mouth and nose during sleep. People snore when they are breathing in or out. Snoring is actually caused by partial upper airway obstruction, and occurs during sleep when the muscles of the upper airway relax. Snoring may affect a large percentage of the population from time to time - up to 30% the population are habitual snorers.
Factors that Cause Snoring
Age - loss of muscle mass as a result of the aging process
Being overweight - fat accumulates on the sides of the upper airway, causing it to become narrow and inclined to close
Sleeping on your back
Enlarged tonsils or adenoids
Alcohol - drinking relaxes the muscles
Use of certain drugs (eg sleeping tablets)
Snoring as a symptom of sleep apnoea
If you snore loudly with occasional pauses in breathing, and frequently wake up during the night, you may have Sleep Apnoea. Ask your partner, or a member of your family, to listen for signs of this disorder.
You can complete an Epworth Sleepiness Scale (overleaf) to asses if you have a sleep disorder.
Sleep disorders are treatable. Your doctor can evaluate your sleep problems with a sleep study and may refer you to a sleep specialist.
(1) Lifestyle Changes
There are several lifestyle changes that can be made to assist in the treatment of snoring. However, except in the mildest cases, additional measures are usually needed. Avoid alcohol and any sedating medications - these can relax the muscles around the upper airway. This may help to decrease the loudness of snoring. If you are overweight, significant weight loss may dramatically reduce the level of snoring. Maintaining this weight loss over time can be difficult for many individuals, but for those who are successful this can be a very effective strategy. Most snorers are loudest while sleeping on their backs, therefore positioning strategies or an extra pillow can help control snoring.
(2) Oral Appliances
These devices are specially designed appliances worn in the mouth during sleep. They maintain an opened, unobstructed airway to alleviate snoring. There are two basic types of oral appliances.
(a) Tongue Retaining Devices
Tongue retainers maintain a forward positioning of the tongue by means of a suction bulb to try and prevent collapse of the upper airway. Very few tongue retainers are available today.
(b) Mandibular Advancement Splints
(MAS) MAS devices work by repositioning and maintaining the lower jaw (mandible) in a protruded position during sleep. This opens the upper airway by tightening the tissues at the back of the throat to allow air to flow freely.
MAS is painless and non-invasive. In addition, therapy is completely reversible and can be used in conjunction with other treatments. If complications arise, the patient can stop wearing the device. Most people find that it only takes a couple of weeks to adjust to wearing the appliances.
(3) Continuous Positive Airways Pressure
Nasal Continuous Positive Airways Pressure (CPAP) is the most common and effective treatment for patients with persistent snoring and sleep apnoea. It prevents airway collapse during use. The patient wears a mask over the nose during sleep, and air is pumped in through the mask into the upper airway. The air splints the muscles in the upper airway and prevents then from collapsing during sleep.
(4) Surgical Treatments
It is difficult to determine with much certainty which procedure is required from the onset,. These procedures have a relatively low success rate in comparison to other treatment options, and are often highly invasive procedures and can be very expensive.
The uvula and portions of the soft palate are removed to widen the airway to help prevent collapse. Since the UPPP only treats the throat walls and has a modest success rate, many surgeons will also perform a procedure to pull the tongue forward at the same time as the UPPP.
Laser assisted UPPP (LAUP)
This is a variation of the UPPP that can be done in the office over several visits. The pain of this procedure and the need for up to five treatments has limited this technique's popularity. Over the last few years, a number of new methods of palatal treatment have been created, all of which are invasive.
Radio frequency waves are used to cause contraction of the excessive tissues and open the upper airway. This is similar to a LAUP.
Maxillo-Mandibular Osteotomy (MMO)
In cases where UPPP and combined procedures have failed, more aggressive surgical approaches have been used. MMO surgery requires cutting the upper and lower jawbones free from their attachments to the skull, pulling them forward and reattaching them in place with metal plates and screws. The teeth remain in good alignment and the net effect is to pull the tongue and its related structures forward, increasing the room in the back of the throat.