ORIGINAL ARTICLE Prevalence of obstructive sleep apnea syndrome in Japanese elementary school children aged 6–8 years Takuro Kitamura & Soichiro Miyazaki & Hiroshi Kadotani & Hideaki Suzuki & Takashi Kanemura & Ichiro Komada & Michiko Nishikawa & Ryuichi Kobayashi & Masako Okawa Received: 3 April 2013 /Revised: 10 June 2013 /Accepted: 5 September 2013 # Springer-Verlag Berlin Heidelberg 2013 Abstract Purpose We aimed to determine the prevalence of and the risk factors for obstructive sleep apnea syndrome (OSAS) in Japanese children aged 6–8 years. Methods The parents of 202 children aged 6–8 years who attended a single elementary school in Shiga, Japan, were requested to complete the Child and Adolescent Sleep Check- list (CASC) and perform home Type 3 portable monitoring of their children. By using the CASC data and monitor record- ings, we estimated the prevalence of pediatric OSAS with the help of different diagnostic criteria and identified the risk factors associated with OSAS. Results Complete data were obtained from 170 of the 194 children whose parents participated in the study. The mean total apnea–hypopnea index and obstructive apnea hypopnea index were 1.4±1.3 and 0.4±0.6 h -1 , respectively, and central apnea was the most prevalent type of respiratory event, ac- counting for 70.4 % of all events. The overall prevalence of OSAS ranged from 0.6 % to 43.5 %, depending on the cutoff value used, and was 3.5 % when using International Criteria of Sleep Disorders version II (ICSD II) diagnostic criteria. The presence of tonsillar hypertrophy was the only parameter whose prevalence was significantly elevated in children with OSAS across all diagnostic criteria. Conclusions The prevalence of pediatric OSAS varies according to the diagnostic criteria used, indicating the need for further research focusing on outcomes to define a clinically significant diagnostic threshold. The presence of tonsillar hypertrophy is an important risk factor in the development of pediatric OSAS. Keywords Apnea . Hypopnea . InternationalClassificationof Sleep Disorders version II . Rhinomanometry . Tonsillar hypertrophy . Type 3 portable monitoring Introduction Obstructive sleep apnea syndrome (OSAS) is associated with prolonged partial upper-airway obstruction and/or intermittent complete obstruction (obstructive apnea) that disrupts normal ventilation during sleep and interferes with normal sleep pat- terns [1]. A common condition in childhood, pediatric OSAS is accompanied by symptoms and signs, such as frequent snoring, and causes neurocognitive impairment, behavioral problems, failure to thrive, hypertension, cardiac dysfunction, and systemic inflammation [2]. Adenotonsillar hypertrophy and obesity are well recognized as important risk factors for pediatric OSAS [1]. Although pediatric OSAS occurs in chil- dren of all ages, it most commonly occurs in young children T. Kitamura (*) : S. Miyazaki : T. Kanemura : M. Okawa Department of Sleep Medicine, Shiga University of Medical Science, Seta Tsukinowa-cho, Otsu, Shiga 520-2192, Japan e-mail: kitamura@med.uoeh-u.ac.jp T. Kitamura : H. Suzuki Department of Otorhinolaryngology, University of Occupational and Environmental Health, Kitakyushu, Japan H. Kadotani Center for Genomic Medicine, Kyoto University Graduate School of Medicine, Kyoto, Japan I. Komada Department of Otorhinolaryngology, Social Insurance Shiga Hospital, Otsu, Shiga, Japan M. Nishikawa Department of Otorhinolaryngology, Ohmikusatsu Tokushukai Hospital, Kusatsu-shi, Shiga, Japan R. Kobayashi Sleep Disordered Breathing Center, Ayagawa National Health Insurance Sue Hospital, Ayagawa, Kagawa, Japan Sleep Breath DOI 10.1007/s11325-013-0893-5