Childhood Sleep Apnea Linked to Brain Damage, Lower IQ

In what is believed to be the first study showing neural changes in the brains of children with serious, untreated sleep apnea, Johns Hopkins researchers conclude that children with the disorder appear to suffer damage in two brain structures tied to learning ability.

Writing in the Aug. 22 issue of the global online journal Public Library of Science Medicine, the Hopkins investigators say they compared 19 children with severe obstructive sleep apnea (OSA) to 12 children without the disorder. Using a special type of MRI, researchers identified changes to the hippocampus and the right frontal cortex. Next, using IQ tests and other standardized performance tests that measure verbal performance, memory and executive function, researchers were able to link the changes in the two brain structures to deficits in neuropsychological performance.

The hippocampus, a structure in the temporal lobe, is vital to learning and memory storage, while the right frontal cortex governs higher-level thinking, such as accessing old memories and using them in new situations.

"This should be a wake-up call to both parents and doctors that undiagnosed or untreated sleep apnea might hurt children's brains," says lead author Ann Halbower, M.D., a lung specialist at the Johns Hopkins Children's Center. "This is truly concerning because we saw changes that suggest brain injury in areas of the brain that house critical cognitive functions, such as attention, learning and working memory."

While researchers have known for years that fragmented sleep, interrupted breathing and oxygen deprivation - all hallmarks of sleep apnea - harm children's learning ability and school performance, this is the first time they have linked changes in the brain's chemistry to the syndrome in children, Halbower believes.

"We cannot say with absolute certainty that sleep apnea caused the injury, but what we found is a very strong association between changes in the neurons of the hippocampus and the right frontal cortex and IQ and other cognitive functions in which children with OSA score poorly," Halbower says.

Children with OSA had lower mean IQ test scores (85) than children without OSA (101). Children with OSA also performed worse on standardized tests measuring executive functions, such as verbal working memory (8 versus 15) and word fluency (9.7 versus 12).

Using magnetic resonance spectroscopic imaging, which plots peak levels of brain chemicals in the form of graphs, researchers compared the ratios between each two of three chemicals - N-acetyl aspartate (NAA), creatine and choline - in children with apnea and in those without. The hippocampus and the right frontal cortex of children with sleep apnea showed altered ratios of these neurochemicals that are not specific to any one disease but indicate injury to brain cells. Next, researchers plan to study whether the ratios will return to normal once the sleep apnea is treated.