Sleep apnoea linked to stuttering and brain damage
12:45 19 November 02
NewScientist.com news service
People with sleep apnoea are much more likely to have stuttered as children - and early brain damage could explain the link. The new finding represents a shift in understanding of what causes the devastating sleep disorder, the team says.
Brain scans conducted by a team led by Ronald Harper at the University of California, Los Angeles, showed that patients with obstructive sleep apnoea also had damage in regions that regulate breathing and speech. The researchers also found that almost 40 per cent of the sufferers stuttered as children, compared with an average of just seven per cent of the general population.
"For decades, we have blamed sleep apnoea solely on a narrowed airway caused by enlarged tonsils, a small jaw or excess fat in the throat," says Harper. "Our findings show that sleep apnoea patients also suffer disordered wiring in brain regions that control muscles of the airway. These glitches may lead to the syndrome, which is exacerbated by a small airway."
Sleep apnoea causes explosive snoring and extreme daytime sleepiness. Patients can wake hundreds of times each night, as muscles in their mouth and throat relax to such an extent that their airway collapses. They have to wake up to resume breathing.
Harper's team used magnetic resonance imaging (MRI) to compare the brains of 21 men with the disorder and 21 healthy men. The patients' scans revealed deficits in multiple regions linked to speech production, movement and emotion, including the frontal and parietal cortex and cerebellum.
These regions were between two and 18 per cent smaller in the patients, and the amount of brain damage correlated directly with the severity of their disorder. The team also found that 38 per cent of the patients had stuttered as children and that some still had language difficulties.
"Our findings suggest this sleep apnoea is a pre-existing condition - that abnormal brain wiring from childhood contributes to the onset of the disorder in adulthood," says team member Paul Macey.
The researchers also noted that the sleep apnoea patients showed difficulties with memory, thought and motor skills. "The repeated oxygen loss from sleep apnoea may damage other brain structures that regulate memory and thinking," suggests Harper.
People with sleep apnoea have an increased risk of high blood pressure, stroke and other heart-related problems. Doctors might now be able to use childhood stuttering as a predictor of later sleep apnoea, says the team.
Although the underlying cause appears to be brain damage, surgery on the mouth and throat might still help some sufferers, they think.
Journal reference: American Journal of Respiratory and Critical Care Medicine (vol 166, p 1382)