Cardiovascular Complications of Obstructive Sleep Apnea Syndrome: Evidence from Children Rakesh Bhattacharjee, Leila Kheirandish-Gozal, Giora Pillar and David Gozal Obstructive Sleep Apnea Syndrome (OSAS) is a common condition in children, and is characterized by intermittent partial or complete occlusion of the upper airway during sleep, leading to profound disturbances in homeostatic gas exchange, fre- quent arousals and disturbed sleep architecture. Pediatric OSAS is associated with a multitude of end-organ morbidities, most of which have been uncovered in the last decade. Of particular interest are the cardiovascular complications that may develop in children with OSAS, since they are posited to have not only an immediately significant impact on cardiovascular health during childhood, but may also affect cardiovascular outcomes later during adult life. In this review, we will present the specific cardiovascular complications that have thus far been described in children with OSAS, with reference to pertinent mechanisms, and potential implications. © 2009 Elsevier Inc. All rights reserved. A lthough the clinical entity of obstructive sleep apnea syndrome (OSAS) was initially described by McKenzie 1 in 1880; almost a complete century elapsed before this condition was ultimately recognized in children. 2 In fact, contrary to popular opinion, snoring during sleep, the hallmark indicator of increased upper airway resistance, is an extremely frequent occurrence during childhood, with up to 27% of children being affected occasionally, and 7% to 12% reporting habitual snoring, that is, loud snoring recognized by parents 3 times or more per week. 3-11 Improved awareness and recogni- tion of OSAS in recent years, particularly regarding the potentially adverse consequences of the disease, have revealed OSAS as a highly prevalent disorder, with an estimated frequency of 2% to 3% using more stringent criteria. 12,13 In children, the symptoms of OSAS are often subtle and do not exhibit uniquely specific features that would make such symptoms imme- diately recognizable, thereby leading to a relative inaccuracy of history and physical examination in the prediction of OSAS, such that polysomnogra- phy is required for the definitive diagnosis of OSAS and its severity. 14 Snoring indicates the presence of heightened upper airway resistance and should therefore be considered abnormal. However, there is still substantial debate as to what is the polysomnographic cutoff that defines clinically relevant OSAS. As will be discussed later, there is evidence that even habitual snoring alone, in the absence of any other gas exchange or sleep architecture abnormality, may be associated with increased risk for neurobehavioral distur- bances. 15 As part of the OSAS spectrum of severity, upper airway resistance syndrome and another polysomnographic feature of obstructive From the Kosair Children's Hospital Research Institute; Division of Pediatric Sleep Medicine, Department of Pediatrics, University of Louisville, Louisville, KY; and Sleep Laboratory, Meyer Children's Hospital, Rambam Medical Center, Haifa, Israel. RB is supported by a post-doctoral fellowship in Sleep Medicine from Jazz Pharmaceuticals. LKG is supported by an investigator-initiated grant from Merck Company and by a grant from the National Space Agency (NNJ05HF 06G). DG is supported by grants from the National Institutes of Health (HL65270 and HL83075), The Children's Foundation Endowment for Sleep Research, and The Commonwealth of Kentucky Research Challenge Trust Fund. Address reprint requests to David Gozal, Kosair Children's Hospital Research Institute, and Division of Pediatric Sleep Medicine, Department of Pediatrics, University of Louisville, Louisville, KY 40202. E-mail: d0goza01@louisville.edu 0033-0620/$ - see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.pcad.2008.03.002 Progress in Cardiovascular Diseases, Vol. 51, No. 5 (March/April), 2009: pp 416-433 416