Dietary intervention combined with exercise improves vascular dysfunction but also obstructive sleep apnea in obese children.

Improves Vascular Dysfunction but Also Obstructive Sleep Apnea in Obese Children To the Editor: We write in response to the article “Effects of Diet and Exercise on Obesity-Related Vascular Dysfunction in Children” by Woo et al.1 We agree with the conclusion of Woo et al that diet and exercise should be regarded as an important strategy to reduce the risk of arterial dysfunction in obese children. However, we believe Woo et al overlooked the important issue of obstructive sleep apnea syndrome (OSAS) in obese children. Woo et al used a prospectively defined value based on US reference data, ie, body mass index (BMI) 23, to define obesity. A fixed BMI value should not be used in children for defining obesity because the normal range of BMI varies with age and gender. Moreover, data from the United States cannot be used as an international reference.2 For Hong Kong, local data are available, and the value for obesity is the 97th percentile of BMI.3 OSAS affected 13% to 36% of obese children.2 Nieto et al4 and Ip et al5 found that OSAS is a potent risk factor of endothelial dysfunction as measured by flow-mediated vasodilatation. Hence, OSAS represented an important confounding factor that was completely ignored in the study by Woo et al. Exclusion of known medical diseases will not exclude OSAS, which is usually asymptomatic in children. The “gold standard” for screening of OSAS in children is sleep polysomnography. Nonetheless, habitual snoring and observed apnea were shown to be important symptoms of OSAS. To exclude the effect of OSAS, Woo et al should at least exclude those with these two symptoms. We believe that a considerable portion of obese children enrolled in the study by Woo et al had undiagnosed OSAS. We suspect that the mechanism of reversibility of obesity-related vascular dysfunction discovered in their study was favorably affected by the improvement of OSAS, as previous studies have shown that weight reduction alone can reverse OSAS.