On regular trips to Sydney, Mr Noble's wife Tamara would look at him and ask: ''Are you asleep?''

As well, the moment the Fyshwick businessman stopped being busy at work he would have to fight to stay awake.

The problem is not uncommon. Port Macquarie businessman Michael Cusato fell asleep after he switched his Cessna 210 to auto-pilot and listened to country and western music on a flight from Port Macquarie to Bankstown airport.

When he realised where he was he was well into the flightpaths of jets. The episode in September last year is under investigation.

Poor alertness causes an estimated 25,000 serious road accidents in Australia every year. Fortunately Mr Noble became aware of his sleep apnoea before he joined the statistics.

''I was not as focused at work, I would forget things, I wasn't as accurate as I had been in the past,'' Mr Noble said.

While seeking help for another condition, he was also referred to Dr Grant Willson, a physiotherapist and sleep clinic director.

Overnight sleep monitoring revealed he was experiencing 97 blockages an hour.

''That means, effectively, I wasn't sleeping at all. I might have my eyes closed, but I wasn't getting any sleep,'' Mr Noble said.

Dr Willson said while more people were undergoing sleep study, doctors and the community needed to be educated about the problem.

''We need to make people aware persistent snoring is not normal and that apnoea, high blood pressure, unrefreshing sleep, persistent tiredness and nocturia (getting up to the toilet at night) may be suggestive of sleep apnoea and should be investigated.''

He expects treatment take-up will grow substantially because studies show the rates of sleep apnoea are huge and have increased over the past 20 years, probably due to weight increase.

Dr Carol Huang of the Department of Respiratory Medicine, Canberra Hospital, says sleep apnoea affects 25 per cent of men and 10 per cent of women.

''The majority of our patients come complaining of snoring,'' Dr Huang said. ''Sometimes their partners complain that they stop breathing during sleep, daytime sleepiness, sometimes just irritability, mood disturbance.

''We sometimes get referrals where people are not sleepy but are complaining of poor concentration, poor memory.''

Prescribed CPAP (continuous positive airway pressure) treatment, Mr Noble straps on a mask each night across his nose, attached to a machine pushing air through tubing to the mask.

The air then passes through the nose and into the throat, where the slight pressure keeps the upper airway open.

''Within a week I was feeling 100 times better. Refreshed, ready to go, that's a hell of a difference to someone waking up tired, with headaches, just not ready to go.

''It means I can get on with my life, get everything done.

''I no longer cause my wife any grief whatsoever in terms of panicking about whether I am going to fall asleep at the wheel, in the middle of a conversation, too tired to get up and do anything.''