According to a new study of children ages 5 to 7,C-reactive protein, a marker of inflammation that is often used to detect cardiovascular disease, may also indicate cognitive impairment in children with obstructive sleep apnea.
"Children with OSA have increased levels of hsCRP [high-sensitivty C-reactive protein] and also exhibit decreased cognitive performances," said lead researcher David Gozal, M.D., of the University of Louisville in Kentucky. "Furthermore, hsCRP levels are significantly increased among patients with OSA and cognitive dysfunction."
These findings were published in the second issue of the July American Journal of Respiratory and Critical Care Medicine, published by the American Thoracic Society.
To identify children for the study, parents in the Jefferson County (KY) Public School system were invited to complete a questionnaire about their children's sleeping habits. Responses indicating almost no likelihood of OSA and those indicating a high likelihood of OSA were randomly selected, and the children were invited to a sleep research center.
Obese children were excluded from the study, because the condition "is now viewed as a low-grade systemic inflammatory disorder, and is associated with increased risk for cognitive deficits."
At the sleep center, the children underwent overnight polysomnographic assessment and then, in the morning, completed tests to determine their reasoning and conceptual abilities.
The results of the individual tests were aggregated into a General Conceptual Ability (GCA) score, with a mean of 100 and a standard deviation of 15 Of a total of 278 children who completed all phases of the evaluation, 73 served as controls. They had no evidence of OSA and their cognitive scores were all normal.
Among the 102 children with OSA, 57 had GCA scores less than 85 percent. The mean level of hsCRP in children with OSA and abnormal scores was approximately 250 percent higher than the control group and approximately 200 percent higher than the level for children with OSA who did not exhibit cognitive impairment.
The authors suggest that an important question yet to be answered is whether OSA treatment would eliminate any cognitive deficits. They cite an earlier study they conducted which found that after an adenotonsillectomy, hsCRP levels in children with OSA were usually reduced.
According to the authors, however, the current findings "reinforce the concept that systemic inflammation is a constitutive component and consequence of OSA" and that the "presence of increased systemic inflammation, as dictated by hsCRP levels and potentially the levels of other inflammatory markers, will increase the probability for decreased neurocognitive function."