Employees may not know they have the condition, but it could affect anyone, experts have warned. Sufferers of sleep apnoea, normally snorers, are unaware of their windpipe narrowing and airflow being blocked for up to a minute, causing blood oxygen levels to fall.
Then the brain awakens the sleeper enough for them to snort or gasp and get air. They then go to sleep and the process begins again. Dr Paul Jackson, who heads Awake, a motor industry consultancy that offers a practical interpretation of the results of work at the Loughborough Sleep Research Centre, said: 'It can happen up to 500 times in a night. Companies need to identify drivers with the problem and take action to help them.'
Male drivers who snore, are 50-plus, overweight and have a collar size of 17 or more are most likely to suffer from sleep apnoea.
Jackson said: 'The next day, sufferers feel tired, fed up, irritable or depressed because they have not slept as well as they thought.
'Often, they are thought of as dopey by their work colleagues because they go to sleep during the day.'
About 5% of people in the UK have sleep apnoea and most of them are men, though many are undiagnosed.
Awake is running a campaign to make business drivers and their employers aware of sleep apnoea. Drivers are vulnerable to the condition, particularly if they spend long periods of time behind the wheel, without exercise. Jackson added: 'Sleep apnoea can also lead to high blood pressure which increases the risk of heart disaease.
'It is important not to go in heavy-handed with staff – you must take people with you by offering optional screening and reassuring them.'
Mild cases can be helped with weight loss and advising patients to sleep on their backs.
Immediate help for more severe cases comes from using a machine that pumps air through a mask to keep airwaves open.