Sleep apnea has been linked to learning impairment, stroke and premature death. Researchers have now found that snoring associated with sleep apnea could impair brain function more than previously thought.

The research shows that sufferers of obstructive sleep apnea experience similar changes in brain biochemistry as people who have had a severe stroke or who are dying.

The study is reportedly the first to analyze what is happening in the brains of sleep apnea sufferers as they sleep. Previous studies have focused on recreating oxygen impairment in awakened patients.

"It used to be thought that sleep apnea snoring had absolutely no acute effects on brain function but this is plainly not true," said lead author of the study, Professor Caroline Rae.
Sleep apnea affects as many as one in four middle-aged men, with around three percent going on to experience a severe form of the condition characterized by extended pauses in breathing, repetitive asphyxia and sleep fragmentation.

Children with enlarged tonsils and adenoids are also affected, raising concerns of long-term cognitive damage.
Professor Rae and fellow researchers used magnetic resonance spectroscopy to study the brains of 13 men with severe, untreated, obstructive sleep apnea. They found that even a moderate degree of oxygen desaturation during the patients' sleep had significant effects on the brain's bioenergetic status.

"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 you are asleep," Professor Rae said.

"A lack of oxygen in the brain during even small time increments of obstructive sleep apnea 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 oxygene depletion," Professor Rae explained.

"This is happening in someone with sleep apnea acutely and continually when they are asleep. It's a completely different biochemical mechanism from anything we've seen before and is similar to what you see in somebody who has had a very severe stroke or is dying."

Professor Rae said it was still unclear why the body responded to oxygen depletion in this way. 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.

"The brain could be basically resetting its bioenergetics to make itself more resistant to lack of oxygen," Professor Rae said. "It may be a compensatory mechanism to keep you alive, we just don't know, but even if it is it's not likely to be doing you much good."
References:
1. Caroline Rae, et al. Journal of Cerebral Blood Flow and Metabolism.