title: Evening chronotype is associated with metabolic disorders and body composition in middle-aged adults.
abstract: BACKGROUND
  Chronotype is a trait determining individual circadian preference in behavioral and biological rhythm relative to external light-dark cycle. However, little is known about the relationship between chronotype and metabolic disorders.
  
  
  OBJECTIVE
  The aim of this study was to examine whether late chronotype is related to metabolic abnormalities and body composition in middle-aged adults, independent of sleep duration and lifestyle.
  
  
  METHODS
  A total of 1620 participants aged 47-59 years were recruited from the Korean Genome and Epidemiology Study.
  
  
  METHODS
  Chronotype was assessed by the Morningness-Eveningness Questionnaire. Associations of chronotype with diabetes, metabolic syndrome, sarcopenia, and visceral obesity were analyzed. All participants underwent the oral glucose tolerance test, and body composition was measured with dual energy x-ray absorptiometry. Visceral obesity was designated as visceral fat area, measured by abdominal computed tomography, of >100 cm(2).
  
  
  RESULTS
  Chronotype was classified as morning in 29.6% of subjects, evening in 5.9%, neither morning nor evening in 64.5%. Evening type, when compared with morning type, was significantly associated with diabetes (odds ratio [OR], 1.73; 95% confidence interval [CI], 1.01-2.95), metabolic syndrome (OR, 1.74; 95% CI, 1.05-2.87), and sarcopenia (OR, 3.16; 95% CI, 1.36-7.33) after adjusting for confounding factors. Gender differences in the associations were evident. In men, evening type was associated with diabetes (OR, 2.98; 95% CI, 1.39-6.39) and sarcopenia (OR, 3.89; 95% CI, 1.33-11.33). Only metabolic syndrome was associated with evening type in women (OR, 2.22; 95% CI, 1.11-4.43).
  
  
  CONCLUSIONS
  At the population level, evening chronotype was independently associated with diabetes, metabolic syndrome, and sarcopenia. These results support the importance of circadian rhythms in metabolic regulation.
authors.affiliation: Division of Endocrinology and Metabolism (J.H.Y., J.H.A., H.J.C., S.K.L., H.J.Y., J.A.S., S.G.K., K.M.C., S.H.B., D.S.C., N.H.K.), Department of Internal Medicine, Korea University College of Medicine, Ansan 425-707, Korea; Department of Neurology (C.-H.Y.), Bundang Clinical Neuroscience Center, Seoul National University Bundang Hospital, Seongnam 463-707, Korea; Department of Psychology (S.S.), Sungshin Women's University, Seoul 136-742, Korea; and the Institute of Human Genomic Study (C.S.), Korea University Ansan Hospital, Korea University College of Medicine, Ansan 425-707, Korea.
authors.forename: Ji Hee
authors.initials: JH
authors.lastname: Yu
authors.forename: Chang-Ho
authors.initials: CH
authors.lastname: Yun
authors.forename: Jae Hee
authors.initials: JH
authors.lastname: Ahn
authors.forename: Sooyeon
authors.initials: S
authors.lastname: Suh
authors.forename: Hyun Joo
authors.initials: HJ
authors.lastname: Cho
authors.forename: Seung Ku
authors.initials: SK
authors.lastname: Lee
authors.forename: Hye Jin
authors.initials: HJ
authors.lastname: Yoo
authors.forename: Ji A
authors.initials: JA
authors.lastname: Seo
authors.forename: Sin Gon
authors.initials: SG
authors.lastname: Kim
authors.forename: Kyung Mook
authors.initials: KM
authors.lastname: Choi
authors.forename: Sei Hyun
authors.initials: SH
authors.lastname: Baik
authors.forename: Dong Seop
authors.initials: DS
authors.lastname: Choi
authors.forename: Chol
authors.initials: C
authors.lastname: Shin
authors.forename: Nan Hee
authors.initials: NH
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D001683:Biological Clocks / Q000502:physiology; D001823:Body Composition; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D006801:Humans; D007206:Individuality; D008019:Life Style; D008297:Male; D008659:Metabolic Diseases / Q000453:epidemiology* / Q000503:physiopathology*; D008875:Middle Aged; D010641:Phenotype; D056910:Republic of Korea / Q000453:epidemiology; D012890:Sleep / Q000502:physiology; D011795:Surveys and Questionnaires