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The sleeper stops breathing for up to two minutes until the body's defence mechanism causes them to wake and breathe normally again. In its mild form, OSA is characterised by snoring and results in disturbed sleep and daytime tiredness. In more severe cases it can lead to obesity, hypertension, bladder problems and death from cardiovascular disease.
Sleep physician Dr Shu Chan says sufferers choke and cease breathing due to obstruction in the throat, which occurs when the muscles controlling the tongue and soft palate relax and the airways narrow. The brain reacts to this oxygen deficiency and alerts the body to wake up. This arousal can happen hundreds of times every night. Sufferers usually feel sleepy and lethargic the next day.
Sleep specialists Dr David Jankelson, at St Vincent's Hospital, and Dr Ron Grunstein, at Royal Prince Alfred (RPA), say it's the most common sleep disorder they treat.
A 1995 study by RPA found OSA affects more than 10 per cent of middle-aged men and 5 per cent of women.
The study notes that this figure is "likely to be a substantial underestimate with the real figure probably being nearer to 30 per cent".
Chan says "the figures are sure to be much larger. Men do not complain, so their sleep apnoea is hidden."
Lack of funding in the area means "we do not have the resources to do the type of comprehensive surveys we need to get the full picture of sleep in Australia," he says.
At St Vincent's, 60 per cent of people treated for sleep disorders have OSA and "the rest would be movement disorder [Restless Leg Syndrome] and respiratory failure," says Jankelson.
Grunstein says OSA is often misdiagnosed and "very much misunderstood". "A lot people don't know what it is [and] sufferers are regarded as lazy, when they are not," he says.
Jankelson says it's not a disorder to be complacent about: "Sleep apnoea has been linked to excessive daytime sleepiness, mood change, irritability, depression and an increased risk of having a motor vehicle accident."
The Medical Journal of Australia recently reported that OSA can increase the risk of accidents by two to seven times.
Chan says many of his patients operate machinery or vehicles, such as train drivers, pilots and defence force personnel. If diagnosed with OSA, they are usually given modified work duties.
Chan calls it adult cot death. "They either recover or have severe problems if sleep apnoea is coupled with chronic lung disease and die in about five years.
"For a lot of sufferers, it is pot luck if you see a GP who knows a respiratory physician. If you live in Sydney and Melbourne you might be lucky but if you live in a regional area it could go unrecognised," he says.
Chan's gloomy prediction for some OSA sufferers is based on research that links the disorder to cardiovascular risks factors, known as "syndrome X" or metabolic dysfunction, which describes a group of related conditions such as insulin resistance, obesity, hypertension and elevated cholesterol.
When OSA is added to the mix, Australian sleep specialists refer to it as "Syndrome Z".
A 2001 study at Johns Hopkins School of Medicine in the United States found "sleep-disordered breathing was associated with impaired glucose tolerance and insulin resistance independent of obesity.
"The implication of these findings is that the metabolic dysfunction associated with sleep-disordered breathing may increase the risk of cardiovascular morbidity and mortality."
Researchers at RPA found "obesity is common in OSA" sufferers and as "body mass increases the incidence of OSA also increases and about 50 per cent of morbidly obese subjects have OSA".
Grunstein, Jankelson and Chan say further research is needed before the link between OSA, cardiovascular disease and obesity is watertight.
Meanwhile, treatment of OSA "is somewhat primitive", says Jankelson.
Many sufferers are prescribed a device called a CPAP (Continuous Positive Airway Pressure), to be worn during sleep, which forces air to the airways through a nasal mask. The upper airways are then kept open, creating an air splint that can prevent OSA and snoring. Its design has been streamlined over the years but is still The paper also explored the link between obesity and OSA. considered unwieldy by physicians and patients.
A study published last year in the American Journal of Respiratory and Critical Care Medicine says: "On average, one-third of patients are non-compliant with CPAP use."
The same paper, however, says use of CPAP may "have long-term beneficial metabolic effects". The rationale that sufferers may lose weight on CPAP arises from studies that links lack of sleep or broken sleep to obesity.
More studies need to be done in this area but obesity can result if there is insufficient oxygen flowing through the body during sleep, says Chan.
The Johns Hopkins study recommends weight loss to reduce OSA: "Because as little as 10 to 15 per cent weight loss can reduce or eliminate sleep-disordered breathing ... and may curtail the cardiovascular risk associated with sleep-disordered breathing."
Grunstein is exploring alternatives to CPAP: "If we had a safe pill, everyone would be treated but we have a limited range of treatment." If a patient is compliant then "CPAP use is 90 to 100 per cent effective," says Jankelson.
Finding a medication is a "slow but promising" process, he says, adding that trials are expected in Australia next year.
Other treatments include dental aids such as plastic splints or the more invasive palatal surgery, as a last resort.
Chan's city office is near Australia Square - a favourite drinking precinct for Sydney's stressed bankers and lawyers.
"I see the young people drinking and partying to release stress after a hard day and I wonder how they sleep," says Chan.
Increasingly, the answer is they don't - or not very well. The average sleep duration has decreased from nine hours in 1910 to seven hours.
More than a third of people experience insomnia at some point but only about 5 per cent need treatment. About two million Australians complain of it each year, costing millions in lost productivity, accidents and health costs.
The pressures of the workplace are often blamed but distractions, such as a television in the bedroom, the internet and computer games, mean the sleep we are getting is of a lesser quality. Chan sees many young people with daytime fatigue. "These kids are subjected to too much stimulation and there are too many things competing for their attention."
Grunstein says that it's not just kids. "What we are seeing is a lot of people who work from home...They get into bed with their laptops and mobiles and do work before they go to sleep and then wonder why they have trouble sleeping."
Chan has seen an increase in insomnia since September 11 and the war in Iraq: "During the Iraqi war some people came in and saw me - they had been crying and said the war was worsening their insomnia. They would sit up all night and watch the war on cable television, then they couldn't sleep because they are going to bed with those images," he says.
Grunstein and Jankelson believe that most insomnia is triggered not by external world events but by an individual's worries and anxieties.
Insomnia can lead to "reactive depression" due to the stress of not being able to sleep, triggering a vicious cycle.
Insomnia should be "primarily managed at a GP level", says Grunstein.
Both RPA and St Vincent's employ psychologists who specialise in insomnia.
The trigger for insomnia can be a stressful or emotional event such as job loss, death of a loved one or divorce.
Grunstein says treatment can include relaxation training, hypnosis, medication and sleep restriction, where "you stimulate the sleep drive by restricting sleep and therefore increase sleepiness".
Jankelson says the incidence of insomnia is increasing but professional services are not keeping up with demand. "There are only one or two sleep psychologists in the city."
He says there's much that individuals can do to help themselves. The doctors call it "sleep hygiene", which is basically a set of rules or behaviour that can lead to a good night's sleep.
"It's about recognising the conditions in which to sleep, such as no drinking alcohol or coffee before bedtime and no TV in the bedroom."
He also recommends having a regular waking time and early morning exercise.
RESTLESS LEG SYNDROME
Restless Leg Syndrome (RLS) is a condition where the sleeper voluntarily moves their leg in response to a tingling sensation.
Sufferers usually feel this before bedtime or when they lie down and the sensations prevent them from relaxing and sleeping.
Chan estimates that 10 per cent of the population suffers some form of RLS or an associated movement disorder.
Treatment is relatively simple using medication, says Chan.
The most serious of the sleep disorders, narcolepsy is a rarity, affecting about 0.05 per cent of adults worldwide. It causes a person to fall asleep without warning. Often the trigger is heightened emotions such as surprise or anger.
Sufferers are treated with amphetamines and Ritalin to keep them alert. A new medication, Modafilil, that promotes wakefulness without the stimulant effect, may provide some relief.
The waking hours
Drinking a few glasses of wine before bed doesn't help you sleep. Instead, it's more likely to interfere with normal sleep patterns, as I discovered when I spent a night in a private inner-city clinic that tests for sleep disorders.
After I arrived at 9pm, two technicians spent 90 minutes preparing me - they put glue in my hair, stuck electrodes to my scalp, suckered them to my forehead and inserted tubes up my nose. Wires across my fingers, legs, feet, chest and waist attached to a machine that pulsated and hummed through the night felt like a tight leash.
Trained on my bed was an infra-red camera and microphone, monitored by a technologist in the next room, who could hear the beating of my heart and watch as I struggled with a heavy quilt.
Jagged brain wave readings recorded the hours spent without sleep.
At 3.30am, uncomfortable, anxious and still awake, I rolled over and pulled out the cords attached to the machine. The technologist ran in and reconnected me.
At 6am breakfast was served. I had slept a measly 103 minutes, in which time the machines picked up a mild case of sleep apnoea.
Expect to pay up to $495 a night for a bed in a private clinic. Medicare and private health funds only cover the pre- and post-sleep consultations.
Stays at St Vincent Hospital's sleep centre are covered by Medicare or private health funds but there is about a four-week wait for a bed.
Patients are referred to the clinic by their doctor.
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