© 2007 American Thoracic Society
Blood Pressure and OSAS in ChildrenFrom the Authors:We thank Dr. Ng and colleagues for their letter commenting on our recent pulmonary perspective (1). Ng and colleagues provide additional data from their own work that underscore two of the premises of our perspective: (1) that children with sleep apnea may suffer a range of comorbidities, including adverse cardiovascular effects such as hypertension, and (2) obesity is a risk factor for sleep apnea in children, albeit the strength of this association likely varies according to the sample characteristics. Although our article, which focused on obesity, did not detail variations reported in vascular tone among children with sleep apnea, we think that the study by Amin and coworkers (2) is important in suggesting that vascular dysregulation, as measured by blood pressure variability and reduced nocturnal dipping, may be an early marker of sleep apnea in pediatric populations. One great advantage of studying cardiovascular responses in children with sleep apnea as compared with adults is the opportunity to identify early pathogenetic responses to recurrent overnight stresses, which may identify a number of abnormalities in autonomic tone, including abnormalities that may precede established daytime hypertension. Ng and coworkers also point out that the strong association relating obesity and sleep apnea in Asian children that we cited was based on the report of Wing and coworkers, which included children referred to an obesity clinic (3), and that others have found lower odds ratios when studying children referred to a sleep clinic. We agree that the strength of associations between risk factors, such as obesity, and health outcomes, such as sleep apnea, may vary greatly according to sampling. We emphasized that differences in reported associations between obesity and pediatric sleep apnea have been commonly reported, and are likely to be partly attributable to age differences across samples, with younger children perhaps more susceptible to airway narrowing due to lymphoid hypertrophy and older children more likely to suffer from more extreme levels of obesity. The stronger association between obesity and sleep apnea reported by Wing and coworkers may be due to their study of older children (mean age approximately 11 yr), as compared with Lam and coworkers (4), who studied children ages 1 to 15 years, with median ages of 6 to 8 years. We also noted that the data suggesting a propensity for Asian children to be at risk for sleep apnea are consistent with other studies suggesting that Asians may be at increased risk for sleep apnea at lower levels of body mass index than their European counterparts, and we emphasize the importance of considering ethnic variations in susceptibility to this disorder. The comments by Ng and coworkers also underscore the relative paucity of pediatric population–based data available to clearly define risk factors and outcomes. Studies of pediatric populations, in whom other comorbidities are generally less frequent than found in adult populations, provide tremendous opportunities to better understand the etiology and adverse effects of both pediatric and adult sleep apnea.
Case Western Reserve University FOOTNOTES Conflict of Interest Statement: Neither author has a financial relationship with a commercial entity that has an interest in the subject of this manuscript. REFERENCES
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