title: The Association between Short or Long Sleep Times and Quality of Life (QOL): Results of the Korea National Health and Nutrition Examination Survey (KNHANES IV-V).
abstract: OBJECTIVE
  Sleep can affect quality of life (QOL). We examined the association between self-reported sleep time and QOL independent of perceived health status and depressive disorder using the EuroQol-5 Dimension (EQ-5D) and a visual analog scale (VAS).
  
  
  METHODS
  We used the nationwide cross-sectional survey data of 28,178 subjects from the Korea National Health and Nutrition Examination Survey (KNHANES) IV-V. Self-reported sleep time was assessed by average hours of sleep per day. QOL was measured using the EQ-5D and VAS. A generalized additive model and multiple linear regression analysis were used to estimate the effect of sleep time on the QOL while adjusting for potential confounding variables.
  
  
  RESULTS
  We found a significant inverted U-shaped relationship between sleep time and QOL using both the EQ-5D and VAS indices. Compared with subjects who slept 7 h/day, Korean men whose sleep time was very short (≤ 4 h/ day) or very long (≥ 10 h/day) had substantially worse QOL (-3.125 in EQ-5D, p < 0.001 and -4.387 on the VAS, p = 0.000 for ≤ 4 h/day; -1.763 in EQ-5D, p = 0.001 and -1.944 on the VAS for ≥ 10 h/day, all p = 0.038). A similar inverted U-shape was observed between sleep time and QOL in Korean women.
  
  
  CONCLUSIONS
  Inappropriate sleep time (either short or long) in both men and women was significantly associated with lower QOL. In particular, such an association was more apparent among persons whose perceived health status was poor.
authors.affiliation: Department of Public Health, Yonsei University, Seoul, Republic of Korea.|Institute of Health Services Research, Yonsei University, Seoul, Republic of Korea.
authors.forename: Jae-Hyun
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Institute of Health Services Research, Yonsei University, Seoul, Republic of Korea.|Department of Preventive Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors.forename: Eun-Cheol
authors.initials: EC
authors.lastname: Park
authors.affiliation: Department of Public Health, Yonsei University, Seoul, Republic of Korea.|Institute of Health Services Research, Yonsei University, Seoul, Republic of Korea.
authors.forename: Ki-Bong
authors.initials: KB
authors.lastname: Yoo
authors.affiliation: Institute of Health Services Research, Yonsei University, Seoul, Republic of Korea.|Department of Biostatistics, Graduate School of Public Health, Yonsei University, Seoul, Republic of Korea.
authors.forename: Sohee
authors.initials: S
authors.lastname: Park
mesh_terms: D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D006304:Health Status; D006306:Health Surveys / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys; D011788:Quality of Life; D056910:Republic of Korea; D012890:Sleep / Q000502:physiology*; D011795:Surveys and Questionnaires; D013997:Time Factors
keywords: EQ-5D; KNHANES; VAS; perceived health status; quality of life (QOL); sleep time