title: Association between self-reported sleep duration and serum vitamin D level in elderly Korean adults.
abstract: OBJECTIVE
  To investigate the association between self-reported sleep duration and serum vitamin D level in elderly Korean adults.
  
  
  METHODS
  Cross-sectional data analysis.
  
  
  METHODS
  Korean National Health and Nutrition Examination Survey 2010.
  
  
  METHODS
  Noninstitutionalized adults aged 60 to 80 (N = 1,614).
  
  
  METHODS
  The confounding variables were serum 25-hydroxy vitamin D level, age, sex, body mass index, smoking history, alcohol consumption, and self-reported daily sun exposure and sleep duration. Self-reported daily sleep duration was divided into four groups: Q1 (≤4 hours), Q2 (5-6 hours), Q3 (7-8 hours), and Q4 (≥9 hours).
  
  
  RESULTS
  Mean serum vitamin D levels of subjects in the Q1, Q2, Q3, and Q4 groups were 44.18, 48.08, 48.83, and 51.78 nmol/L, respectively. On multivariate linear regression analysis, subjects in the Q2 (B = 3.80, 95% confidence interval (CI) = 0.42-7.19), Q3 (B = 4.89, 95% CI = 1.54-8.24), and Q4 (B = 5.18, 95% CI = 0.78-9.58) groups had significantly higher serum vitamin D levels than subjects in the Q1 group.
  
  
  CONCLUSIONS
  Serum vitamin D level is positively associated with self-reported daily sleep duration in elderly Korean individuals. These results suggest that inadequate sleep duration may be associated with lower vitamin D levels in elderly adults.
authors.affiliation: Department of Otorhinolaryngology, School of Medicine, Jeju National University, Jeju, Korea.
authors.forename: Jeong Hong
authors.initials: JH
authors.lastname: Kim
authors.forename: Jung Hyun
authors.initials: JH
authors.lastname: Chang
authors.forename: Dong Young
authors.initials: DY
authors.lastname: Kim
authors.forename: Ju Wan
authors.initials: JW
authors.lastname: Kang
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015986:Confounding Factors, Epidemiologic; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007407:Interviews as Topic; D008297:Male; D008875:Middle Aged; D056910:Republic of Korea / Q000453:epidemiology; D012307:Risk Factors; D012893:Sleep Wake Disorders / Q000097:blood* / Q000453:epidemiology; D011795:Surveys and Questionnaires; D014808:Vitamin D Deficiency / Q000097:blood* / Q000453:epidemiology
keywords: elderly; sleep duration; vitamin D