March 17, 2017 -- A study comparing children between 7 and 11 years of age who have moderate or severe obstructive sleep apnoea to children the same age who slept normally, found significant reductions of gray matter in several regions of the brains of children with sleep apnoea. The study was published today in the journal Scientific Reports.The finding points to a strong connection between this common sleep disturbance, which affects up to 5% of all children, and the loss of neurons or delayed neuronal growth in the developing brain. This extensive reduction of gray matter in children with a treatable disorder provides one more reason for parents of children with symptoms of sleep apnoea to consider early detection and therapy."The images of gray matter changes are striking," said one of the study's senior authors, Leila Kheirandish-Gozal, MD, University of Chicago, Chicago, Illinois. "We do not yet have a precise guide to correlate loss of gray matter with specific cognitive deficits, but there is clear evidence of widespread neuronal damage or loss compared to the general population."For this study, the researchers recruited 16 children with obstructive sleep apnoea (OSA). The children's sleep patterns were evaluated overnight in the University of Chicago's paediatric sleep laboratory. Each child also went through neuro-cognitive testing and had his or her brain scanned with non-invasive magnetic resonance imaging (MRI). Colleagues from the University of California at Los Angeles (UCLA), Los Angeles, California, performed the image analysis.The researchers compared those scans, plus neuro-cognitive test results, with MRI images from 9 healthy children of the same age, gender, ethnicity and weight, who did not have apnoea. They also compared the 16 children with OSA to 191 MRI scans of children who were part of an existing pediatric-MRI database assembled by the National Institutes of Health.They found reductions in the volume of gray matter in multiple regions of the brains of children with OSA. These included the frontal cortices (which handle movement, problem solving, memory, language, judgement and impulse control), the prefrontal cortices (complex behaviours, planning, personality), parietal cortices (integrating sensory input), temporal lobe (hearing and selective listening) and the brainstem (controlling cardiovascular and respiratory functions).Although these gray matter reductions were rather extensive, the direct consequences can be difficult to measure."MRI scans give us a bird's eye view of the apnoea-related difference in volume of various parts of the brain, but they don't tell us, at the cellular level, what happened to the affected neurons or when," said co-author David Gozal, MD, University of Chicago. "The scans don't have the resolution to determine whether brain cells have shrunk or been lost completely," he added. "We can't tell exactly when the damage occurred. But previous studies from our group showed that we can connect the severity of the disease with the extent of the cognitive deficits, when such deficits are detectable."In addition, "we are planning future collaborative studies between the University of Chicago and UCLA that will use state-of-the-art imaging approaches to answer the many questions raised by the current study," said Paul Macey, PhD, who, along with colleague Rajesh Kumar,