"The present study provides some insights into the investigation of the neuropathological mechanism of cognitive dysfunction related to children with OSA," Dr. Jiangang Liu of Beihang University, in Beijing, and colleagues write in the journal Sleep.
Research over the past two decades has suggested that the intermittent hypoxemia and sleep deprivation and fragmentation typical of OSA are associated with cognitive problems in both children and adults with OSA.
In the Chinese study, 20 children with OSA (12 boys; mean age, 7) and 29 healthy volunteers (12 males; mean age, 8) underwent functional-MRI scans to evaluate resting-state brain activity; eight participants with OSA and nine control participants had to be sedated with chloral hydrate.
The team used the Wechsler Intelligence Scale for Children to assess cognitive function.
The amplitude of low-frequency fluctuation in the fMRI signal, which indicates the intensity of spontaneous neural activity, was significantly increased in the right insula, but significantly decreased in the left angular gyrus, in participants with OSA.
In addition, regional homogeneity, which reflects the synchronization of spontaneous neural activity in a brain region, was significantly decreased in the left medial superior frontal gyrus, right lingual gyrus and left precuneus in the patients.
Abnormality in either measure, the authors note, is associated with cognitive deficits.
Full-scale IQ (FIQ) and verbal IQ (VIQ) scores in children with OSA were both significantly lower than those of healthy controls, which suggests "possible impairments of children with OSA in executive function, attention and short-term memory function," the authors say.
Dr. Lisa Matlen, clinical assistant professor of pediatric neurology and sleep medicine at Michigan Medicine, in Ann Arbor, told Reuters Health by email that although she's not an expert in fMRI, it's possible that this is the first fMRI study in children with OSA.
She cautioned, however, that "although specific brain regions were identified as abnormal and also certain cognitive functions were measured abnormal in the OSA group, it does not mean those brain regions are responsible for the impaired cognitive functions."
"I don't think we can directly conclude that lower FIQ/VIQ matches with those brain regions just because of an association between the variables of OSA, change in fMRI activity, and lower FIQ/VIQ in this very small cohort," Dr. Matlen added.
She noted that the findings might guide further research "needed to clarify whether the identified brain regions found to be abnormal on the fMRI are indeed correlated to poor cognitive and/or executive function in kids and also if obstructive sleep apnea causes these changes."
It would be interesting, for example, to track fMRI changes with OSA treatment to see if such changes, if truly significant, might be reversible, Dr. Matlen said. "A direct relationship between OSA and measurable neurologic impairments may perhaps more strongly compel treatment in otherwise equivocal situations."
Dr. Liu and two other corresponding authors did not reply to Reuters Health's request for comment.
SOURCE: https://bit.ly/3toP5lH Sleep, online March 1, 2021.
By Scott Baltic
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