UCLAscientists have discovered that patients suffering from obstructive sleep apneashow gray matter loss in brain areas that regulate breathing and speech. Nearly40 percent of these patients also stuttered as children, suggesting that thenighttime breathing disorder may arise from faulty brain wiring early in life.The study was published in the Nov. 15 edition of the American Journal ofRespiratory and Critical Care Medicine.
"Fordecades, we have blamed sleep apnea solely on a narrowed airway caused byenlarged tonsils, a small jaw or excess fat in the throat," said Dr. RonaldHarper, principal investigator and professor of neurobiology at the DavidGeffen School of Medicine at UCLA. "Our findings show, however, that sleepapnea patients also suffer disordered wiring in brain regions that controlmuscles of the airway. These glitches may lead to the syndrome, which isexacerbated by a small airway."
Harper's team used magneticresonance imaging (MRI) to compare brain structures of 21 men who had been diagnosedwith sleep apnea to 21 men who did not suffer from the disorder. Then theyweighed their findings against a template derived from 152 normal MRI scansobtained from the Montreal Neurological Institute.
Both setsof men were matched for age and weight. The researchers also considered theeffects of disease severity, tobacco use, hypertension, cardiovascular healthand whether the men were left- or right-handed in their comparison.
The MRIsrevealed dramatic gray matter loss in the brains of the men with sleep apnea.Curiously, the tissue loss occurred primarily in regions of the brain thatcontrol speech production, movement and emotion. The amount of brain damagedirectly correlated to the severity of the patient's disorder. The healthymen's brains ranged from 2 percent to 18 percent larger in these areas than themen with sleep apnea.
"We proposethat early damage to the brain's speech center triggers problems in the musclesthat control the airway," said Dr. Paul Macey, first author and assistantresearcher of neurobiology at the David Geffen School of Medicine at UCLA."This, in turn, eventually leads to sleep apnea."
"Our findings suggestthis sleep apnea is a pre-existing condition — that abnormal brain wiringfrom childhood contributes to the onset of the disorder in adulthood," Harpersaid. "The evidence in the brain is very specific."
Harpernoted that obstructive sleep apnea patients often display other traits thatsuggest subtle brain damage, including problems with memory, thought and motorskills. "The repeated oxygen loss from sleep apnea may damage other brainstructures that regulate memory and thinking," he said.
The UCLAresearchers uncovered another intriguing finding. In an online supplement totheir article, Harper and Macey wrote that 38 percent of the sleep apneapatients reported a history of stuttering or speech impairment. Most of the menhad struggled with word-formation problems since childhood, and some still hadlanguage difficulties as adults.
Theincidence of stuttering in the general population is 7 percent.
"Becausethe sleep apnea patients possessed speech impairments from childhood and theirbrain's speech center revealed significant gray matter loss, this brain damagelikely originated early in life," Macey said.
The nextstep will be to examine the brain structures of children afflicted withobstructive sleep apnea, who may not have battled the disease long enough todevelop the brain damage found in adults.
"Speechimpediments may prove an important diagnostic clue for assessing and treatingsleep apnea," Macey said. "In the future, doctors may monitor certain brainstructures and examine children for speech or movement problems that maypredict a higher sleep apnea risk."
Nearly 4 percent of theU.S. population suffers from obstructive sleep apnea, which causes explosivelyloud snoring at night and extreme sleepiness during the day. People who sufferfrom the disorder constantly struggle to breathe during sleep, because theirthroat and mouth relax to such a degree that their airway collapses. They wakeup to begin breathing, then repeat the cycle throughout the night, seriouslydisrupting their sleep.
The loss ofoxygen and the constant struggle to breathe increase sleep apnea patients' riskof high blood pressure, stroke and other heart-related ailments. The disorderis most common in men, the elderly, the obese and children with large tonsils —but not all people with these characteristics develop the disease.
The National Heart, Lung and Blood Institute supportedthe UCLA study. Harper and Macey's co-authors included Luke Henderson,Katherine Macey, Jeffry Alger, Robert Frysinger, Mary Woo, Rebecca Harper andFrisca Yan-Go.