title: Influence of sleep-onset time on the development of 18-month-old infants: Japan Children's cohort study.
abstract: OBJECTIVE
  We report here the influence of sleep patterns on the development of infants in Japan. A total of 479 infants were registered in two different Japanese cities. Direct neurological observations were performed by licensed pediatric neurologists.
  
  
  METHODS
  We designed a prospective cohort study and identified the sleep factors of children showing atypical development. The Kinder Infant Developmental Scale (KIDS) was used to evaluate the infant developmental quotient (DQ); we also applied a neurobehavioral screening battery. Neurobehavioral observations in 18-month-old infants were designed to check all developmental categories within the three areas of motor function, language, and social function. Based on the observations, each infant was classified as having "atypical development" or "typical development".
  
  
  RESULTS
  We found that later sleep onset time (>22:00 h), and longer naps during the day each had significant positive correlations with atypical development patterns in 18-month-old infants. For each hour the infant sleep-onset time extended past 22:00 h, the infants showed worse neurodevelopmental outcomes, at an odds ratio increase of 2.944.
  
  
  CONCLUSIONS
  Although our results may be confounded by sleep problems resulting from pre-existing developmental disabilities, we can safely conclude that appropriate sleeping habits are important for healthy development in 18-month-old infants.
authors.affiliation: Japan Children's Study Group (JCS), Research Institute of Science and Technology for Society, Japan Science and Technology Agency, Tokyo, Japan; Department of Pediatrics and Child Health, Kurume University School of Medicine, Fukuoka, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Iemura
authors.affiliation: Japan Children's Study Group (JCS), Research Institute of Science and Technology for Society, Japan Science and Technology Agency, Tokyo, Japan; Department of Pediatrics and Child Health, Kurume University School of Medicine, Fukuoka, Japan.
authors.forename: Mizue
authors.initials: M
authors.lastname: Iwasaki
authors.affiliation: Japan Children's Study Group (JCS), Research Institute of Science and Technology for Society, Japan Science and Technology Agency, Tokyo, Japan; Clinical Research Institute, Mie-chuo Medical Center, National Hospital Organization, Mie, Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Yamakawa
authors.affiliation: Japan Children's Study Group (JCS), Research Institute of Science and Technology for Society, Japan Science and Technology Agency, Tokyo, Japan; Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Kiyotaka
authors.initials: K
authors.lastname: Tomiwa
authors.affiliation: Japan Children's Study Group (JCS), Research Institute of Science and Technology for Society, Japan Science and Technology Agency, Tokyo, Japan; Ochanomizu University, Tokyo, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Anji
authors.affiliation: Japan Children's Study Group (JCS), Research Institute of Science and Technology for Society, Japan Science and Technology Agency, Tokyo, Japan; Ochanomizu University, Tokyo, Japan.
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Sakakihara
authors.affiliation: Centre for Bio-Statistics, Kurume University School of Medicine, Fukuoka, Japan.
authors.forename: Tatsuyuki
authors.initials: T
authors.lastname: Kakuma
authors.affiliation: Department of Pediatrics and Child Health, Kurume University School of Medicine, Fukuoka, Japan.
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Nagamitsu
authors.affiliation: Japan Children's Study Group (JCS), Research Institute of Science and Technology for Society, Japan Science and Technology Agency, Tokyo, Japan; Department of Pediatrics and Child Health, Kurume University School of Medicine, Fukuoka, Japan. Electronic address: toyojiro@st-mary-med.or.jp.
authors.forename: Toyojiro
authors.initials: T
authors.lastname: Matsuishi
mesh_terms: D002657:Child Development; D002658:Developmental Disabilities / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007223:Infant; D007564:Japan; D008297:Male; D009483:Neuropsychological Tests; D011446:Prospective Studies; D012890:Sleep
keywords: Cohort study; Sleeping habits; Social development