title: Inverse relationship between sleep duration and myopia.
abstract: OBJECTIVE
  To investigate the association between sleep duration and myopia.
  
  
  METHODS
  This population-based, cross-sectional study using a nationwide, systemic, stratified, multistage, clustered sampling method included a total of 3625 subjects aged 12-19 years who participated in the Korean National Health and Nutrition Examination Survey 2008-2012. All participants underwent ophthalmic examination and a standardized interview including average sleep duration (hr/day), education, physical activity and economic status (annual household income). Refractive error was measured by autorefraction without cycloplegia. Myopia and high myopia were defined as ≤-0.50 dioptres (D) and ≤-6.0 D, respectively. Sleep durations were classified into 5 categories: <5, 6, 7, 8 and >9 hr.
  
  
  RESULTS
  The overall prevalence of myopia and high myopia were 77.8% and 9.4%, respectively, and the overall sleep duration was 7.1 hr/day. The refractive error increased by 0.10 D per 1 hr increase in sleep after adjusting for potential confounders including sex, age, height, education level, economic status and physical activity. The adjusted odds ratio (OR) for refractive error was 0.90 (95% confidence interval [CI], 0.83-0.97) per 1 hr increase in sleep. The adjusted OR for myopia was decreased in those with >9 hr of sleep (OR, 0.59; 95% CI, 0.38-0.93; p for trend = 0.006) than in those with <5 hr of sleep. However, high myopia was not associated with sleep duration.
  
  
  CONCLUSIONS
  This study provides the population-based, epidemiologic evidence for an inverse relationship between sleep duration and myopia in a representative population of Korean adolescents.
authors.affiliation: Department of Ophthalmology and Visual Science, College of Medicine, Catholic University of Korea, Suwon, Korea.|Department of Epidemiology and Biostatistics, Harvard School of Public Health, Boston, MA, USA.
authors.forename: Donghyun
authors.initials: D
authors.lastname: Jee
authors.affiliation: Research School of Biology, ARC Centre of Excellence in Vision Science, St. Vincent's Hospital, Australian National University, Canberra, ACT, Australia.
authors.forename: Ian G
authors.initials: IG
authors.lastname: Morgan
authors.affiliation: Department of Ophthalmology and Visual Science, College of Medicine, St. Mary's Hospital, Catholic University of Korea, Buchon, Korea.
authors.forename: Eun Chul
authors.initials: EC
authors.lastname: Kim
mesh_terms: D000293:Adolescent; D001824:Body Constitution; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D009216:Myopia / Q000453:epidemiology* / Q000503:physiopathology; D047728:Myopia, Degenerative / Q000453:epidemiology / Q000503:physiopathology; D009749:Nutrition Surveys; D016017:Odds Ratio; D015995:Prevalence; D056910:Republic of Korea / Q000453:epidemiology; D012890:Sleep / Q000502:physiology*; D012893:Sleep Wake Disorders / Q000503:physiopathology; D013997:Time Factors; D055815:Young Adult
keywords: Korea; high myopia; myopia; sleep