Snoring and sleep apnoea damage the brain

May 17 2009

Australian researchers have found that the effects of sleep apnoea on the brain of a sleeping patient are far worse than previously thought.

Sleep apnoea has already been linked to learning impairment, stroke and premature death but this latest research from the University of New South Wales (UNSW) has revealed that snoring linked to sleep apnoea may impair brain function much more than previously thought.

A study by UNSW Brain Sciences analysed the effects of sleep apnoea on the brain while the patient was sleeping and found that those suffering from obstructive sleep apnoea experience similar changes in brain biochemistry as people who have had a severe stroke or who are dying.

Previous studies have focused on recreating oxygen impairment in awake patients but this new research is the first to analyse - in a second-by-second timeframe - what is happening in the brains of sufferers as they sleep.

Lead author of the study, Professor Caroline Rae says in the past it was thought that apnoeic snoring had absolutely no acute effects on brain function but this is not true.

Sleep apnoea affects as many as one in four middle-aged men, with around 3% developing a severe form of the condition characterised by extended pauses in breathing, repetitive asphyxia and sleep fragmentation.

As children with enlarged tonsils and adenoids are also affected, this new research has raised concerns about the possibility of long-term cognitive damage.

Professor Rae and her researchers from Sydney University's Woolcock Institute used magnetic resonance spectroscopy to study the brains of 13 men with severe, untreated, obstructive sleep apnoea and they found that even a moderate degree of oxygen desaturation during the patients' sleep had significant effects on the brain's bioenergetic status.

Professor Rae, who is based at the Prince of Wales Medical Research Institute, says the findings show that lack of oxygen while asleep may be far more detrimental than when awake, possibly because the normal compensatory mechanisms don't work as well when a person is asleep.

Professor Rae says a lack of oxygen in the brain during even small time increments of obstructive sleep apnoea caused levels of the high-energy currency adenosine triphosphates (ATP) to fall and levels of inorganic phosphate to rise, without the usual changes in phosphocreatine or brain pH - the mechanisms that normally would protect the brain against oxygen depletion - and this is happening in someone with sleep apnoea acutely and continually when they are asleep.

She says it is a completely different biochemical mechanism from anything seen before and is similar to what is seen in somebody who has had a very severe stroke or is dying and the findings suggest societal perceptions of snoring as funny need to change.

Professor Rae says it remains unclear why the body responds to oxygen depletion in this way but it could be a form of ischemic preconditioning at work, much like in heart attack sufferers whose initial attack makes them more protected from subsequent attacks.

Professor Rae suggests that the brain could be basically resetting its bioenergetics to make itself more resistant to lack of oxygen and it may be a compensatory mechanism to keep you alive, but even if this is so, it's not likely to be doing you much good.

The study is published in the May edition of Journal of Cerebral Blood Flow and Metabolism.