The study suggests it cuts off oxygen supply during sleep which can lead to brain damage.
Sleep apnoea is the most common sleep disorder, affecting about 1.5 million Brits, and is treated by wearing a mask in bed that blows air into the back of the throat.
Now the first study of its kind is being launched to see if the therapy prevents dementia – the UK’s biggest killer.
Professor Elizabeth Coulson, of the Queensland Brain Institute at the University of Queensland, said: “Treating sleep apnoea may reduce dementia risk.
“People who suffer from sleep apnoea are two to three times more likely to develop Alzheimer’s disease.
“This could be because hypoxia – lower levels of oxygen in the blood from poor breathing – causes nerve cell death.”
The condition is caused when the muscles and soft tissue in the throat relax, causing a blockage of the airways.
It interferes with breathing, often stopping it altogether for short periods many times a night leading to lack of oxygen, restless sleep and heavy snoring.
The condition blights the lives of about one in 20 people – five per cent of the population. Twice more common in men than women, it can begin at any time, including childhood. Many sufferers are unaware they have it.
So Prof Coulson and colleagues are enrolling sleep apnoea patients aged 55 to 75 to see if wearing the CPAP (Continuous Positive Airways Pressure) mask stops or slows brain degeneration.
The team found inadequate oxygen levels during sleep can harm and neurons and raise the risk of developing Alzheimer’s.
Prof Coulson explained people sleep apnoea results in lower levels of oxygen in the blood, known medically as hypoxia. This can triple the risk of Alzheimer’s. The researchers have been investigating the mechanisms by which this occurs, finding hypoxia leads to the degeneration of an area of the brain important for attention and learning.
Prof Coulson said sleep apnoea affects more than a million Australian adults, and is usually treated with CPAP.
It consists of a plastic mask that fits over the nose and mouth and is connected to a machine that blows air under low pressure continually into the back of the throat,
Prof Coulson said this keeps the airway open, helps maintain correct oxygen levels and, ultimately allows for a better quality sleep.
The response is immediate and obvious after only a few hours or one night.
He said: “The next stage of our research involves following patients with sleep apnoea over an extended period of time to determine whether CPAP protects against cognitive decline.”
Sleep apnoea is a serious condition which can lead to other problems such as high blood pressure, which in turn can lead to strokes and heart attacks.
Professor Pankaj Sah, director of the Queensland Brain Institute, said the research could lead to initiating early intervention in patients.
He added: “Sleep disturbances can occur up to 10 years prior to Alzheimer’s disease.
“Considering that Alzheimer’s affects roughly one third of the elderly population, this important research may inform preventative public health measures in the future.”
Sleep apnoea causes excessive sleepiness and tiredness during the day so that people often fall asleep at work, during meals or even standing up.
In drivers or people working with heavy machinery the dangers are clear.
There is good evidence to show that the incidence of road accidents is high in individuals with the condition.
It also means that people become depressed or bad tempered and lacking in concentration, disrupting their social lives and relationships.
Alzheimer’s is the most common form of dementia and now affects more than 500,000 people in the UK – a figure expected to triple by 2050. Dementia affects the ability to remember, think and reason.