Untreated sleep apnoea in children can harm brain cells tied to cognition and mood.
A study comparing children between 7 and 11 years of age who have moderate or severe sleep apnoea to children the same age who slept normally, found significant reductions of grey matter (brain cells involved in movement, memory, emotions, speech, perception, decision making and self-control) in several areas of the brains of children with sleep apnoea.
The finding points to a strong link between the common sleep disorder, which affects up to 5% of all children, and the loss of neurones, or delayed neuronal growth, in the developing brain. This extensive reduction of grey matter in children with a treatable sleep disorder provides one more reason for parents of children with symptoms of sleep apnoea to consider early detection.
Dr David Gozal, professor of paediatrics at the University of Chicago, says the MRI images paint an important picture,
“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 neurones or when.
The scans don’t have the resolution to determine whether brain cells have shrunk or been lost completely. 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.”
The study, published this week in the journal Scientific Reports, looked at 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).
The researchers compared those scans, plus neuro-cognitive test results, with MRI images from nine 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 paediatric-MRI database assembled by the National Institutes of Health.
They found reductions in the volume of grey matter in multiple regions of the brains of children with apnoea. These included the frontal cortices (which handle movement, problem solving, memory, language, judgement and impulse control), the prefrontal cortices (complex behaviors, planning, personality), parietal cortices (integrating sensory input), temporal lobe (hearing and selective listening) and the brainstem (controlling cardiovascular and respiratory functions).
Dr Leila Kheirandish-Gozal, director of paediatric clinical sleep research at the University of Chicago, explained why the finding is important,
“If you’re born with a high IQ – say 180 – and you lose 8 to 10 points, which is about the extent of IQ loss that sleep apnoea will induce on average, that may never become apparent.
But if your IQ as a child was average, somewhere around 90 to 100, and you had sleep apnoea that went untreated and lost 8-10 points, that could potentially place you one standard deviation below normal. No one wants that.”
Or, it may just be too soon to measure. The children in this study were between 7 to 11 years old. The connections between greater grey matter volume and intelligence have been documented only in children with an average age of 15.4 years.
The researchers suggest that the new evidence should prompt “intensive future research efforts” into chronically disrupted children’s sleep.
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