Like adults, children can suffer from sleep-disordered breathing (SDB) such as snoring or obstructive sleep apnea (OSA). In new research published in the November issue of the American Thoracic Society’s American Journal of Respiratory and Critical Care Medicine, scientists explore the interaction between sleep, breathing, and brain function and find that about two-thirds of children with SDB have some degree of cognitive deficit. The new study finds that is quite difficult to correlate the severity of the cognitive deficit to the severity of the SDB, possibly because other crucial issues are involved or because researchers are not measuring the correct factors.
Principal investigator Raouf Amin, M.D. (professor of pediatrics and director, Division of Pulmonary Medicine at Cincinnati Children’s Hospital Medical Center) said that, “A history of snoring is a predictor for cognitive deficit in children with SDB.” He added: “However, the frequency of apnea events during sleep does not predict cognitive deficit and does not correlate with the degree of cognitive deficit. Such a paradox raised the question of whether there are some variables that we do not traditionally measure in the sleep laboratory that might modify the effect of SDB on cognition.”
The research of Dr. Amin and colleagues used a new measurement of the degree to which the brain’s blood remains oxygenated during sleep. This new parameter was included in the analysis of SDB to see if it could better explain the variability in the severity of SDB that is related to cognitive dysfunction. A technology that penetrates the skull with high-powered light beams – near infrared spectroscopy – was used to assess oxygen saturation in children age 7 to 13 years old with varying degrees of SDB; this measurement is called “regional cerebral oxygen concentration” (SrO2). In addition, the researchers measured blood pressure (BP) during sleep.
Amin and colleagues found a positive relationship between snoring and lower regional cerebral oxygen concentrations in healthy children. Strangely and paradoxically for the authors, there were higher regional cerebral oxygen concentration levels in children with sleep apnea, a condition normally considered a more severe degree of SDB, compared with children who only snored.
“During normal sleep, when breathing appears to be stable, there seems to be higher oxygen in the brain among children with sleep apnea compared even to normal children,” clarified Dr. Amin. The authors suggest that their unexpected finding is partially due to the higher blood pressure of sleep apnea sufferers. “Children with sleep apnea have higher BP compared to children with snoring. This may explain why paradoxically we find higher oxygen levels in children with OSA.”
David Gozal, M.D. (professor of pediatrics and director, Kosair Children’s Hospital Research Institute, University of Louisville) wrote in an accompanying editorial that, “It shows us that what is happening in children with OSA and that neurocognitive deficits are not just in the brain matter but involve the cardiovascular system as well.”
Dr. Gozal concludes by noting how this study brings up more issues regarding the link between SDB and cognitive deficits in children that are worthy of investigation. Prevention and treatment efforts will rely on our understanding of the source of the association.
“By taking into account the role of blood pressure in regulating the amount of oxygen concentration in the brain, we might have a better understanding of the relationship between sleep-disordered breathing and cognitive deficit,” concludes Dr. Amin.
Determinants of Regional Cerebral Oxygenation in Children with Sleep-disordered Breathing
Maha Abou Khadra, Keith McConnell, Rhonda VanDyke, Virend Somers, Matthew Fenchel, Syed Quadri, Jenny Jefferies, Aliza P. Cohen, Michael Rutter, and Raouf Amin
American Journal of Respiratory and Critical Care Medicine (2008): Vol 178, pp 870-875
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Written by: Peter M Crosta