RANCHO MIRAGE, CALIF. — Obstructive sleep apnea in children is associated with profound deficits in IQ, verbal comprehension, perceptual reasoning, and working memory, according to preliminary results of a case-control study at the Pediatric Sleep Disorders Center of Johns Hopkins University, Baltimore.
Ann C. Halbower, M.D., medical director of the center, reported that extensive cognitive deficits and cerebral metabolite alterations were powerfully evident in children from inner city Baltimore who suffered from moderate to severe obstructive sleep apnea (OSA).
Thus far, 17 children aged 7–16 years with OSA and 10 matched controls have completed sleep studies, neuropsychological tests, and magnetic resonance spectroscopy. The average age in both groups is 10.
“Our kids with OSA were severely impacted, their IQ scores being 10 to 15 or more points below normal. We saw huge differences in memory, especially in visual spatial processing, which is a parietal lobe function that has not received a lot of press,” Dr. Halbower said at a conference on sleep in infancy and childhood sponsored by the Annenberg Center for Health Sciences.
Group differences in IQ were mostly explained by sharply defined deficits in working memory, nonverbal reasoning, and verbal comprehension among children with OSA.
Magnetic resonance spectroscopy determined that neuropsychological deficits in the children correlated with hippocampal metabolite alterations, low oxygen saturation, and body mass index (BMI).
The study is ongoing, although Dr. Halbower said she and her team are having trouble finding normal, nonsnoring obese controls who do not have sleep apnea. The average BMI among children with OSA was 29 and among controls, 19. African American children whose mothers completed about 12–14 years of education comprise the majority of the study cohort.
Subjects in the control group had significantly higher IQs than did those with OSA, but still not as high as controls enrolled in previous studies of sleep apnea. The mean full-scale IQ among controls was 101, and among children with OSA, 86.
Children with an IQ below 75, a history of seizures or depression, or use of psychotropic medications were not enrolled.
Intriguingly, some of the neuropsychological functions most impacted by sleep apnea in adults were not significantly impaired in children with OSA. These included certain executive functions such as problem solving, planning, inhibitory control, sustained attention, and response preparation. Motor speed and cerebellar perceptual/motor timing appeared unaffected as well.
When respiratory parameters were assessed, children with OSA had a mean oxygen desaturation time at less than 95% of 70 minutes, compared with 0 for controls. To capture small, brief, intermediate hypoxic events, the oxygen saturation nadir also was studied, and was 75 for children with OSA and 93 for controls, a statistical difference with a significance of 0.0002.
The apnea/hypopnea index showed that children in the study had severe OSA, with a mean score of 29.1, compared with 0.3 for controls.
Researchers conducted two forms of magnetic resonance spectroscopy to attempt to pinpoint any cerebral metabolite changes that might be correlated with respiratory parameters and neuropsychological test results. A global brain assessment was conducted with general magnetic resonance spectroscopy imaging (MRSI) and a single voxel image was used to explore metabolites within the anterior hippocampus on the left side.
Just six children with OSA and six controls have completed these studies.
However, preliminary results identified a “very significant” decline in N-acetyl aspartate/choline (NAA/Cho) ratios and choline/creatine (Cho/Cr) ratios in the hippocampal regions of children with OSA, compared with controls.
Both oxygen saturation nadir and oxygen saturation time at less than 95% correlated with brain metabolite dysfunction, IQ deficits, and BMI.
The apnea/hypopnea index correlated with brain metabolite problems, IQ problems, parietal lobe function problems, and BMI; however, the arousal and awake index failed to correlate with brain metabolite dysfunction, IQ, or BMI, “indicating that hypoxemia may be involved in the mechanism of these alterations,” said Dr. Halbower.
Of interest, high BMI correlated with IQ deficits and low neuropsychological scores, but not with brain metabolites. The issue deserves further study, she said.
More subjects are being enrolled in the current investigation and researchers also are exploring possible reversibility of neurologic deficits with treatment of OSA.