title: Sleep time and cardiovascular risk factors in adolescents: the HELENA (Healthy Lifestyle in Europe by Nutrition in Adolescence) study.
abstract: OBJECTIVE
  We aimed to examine the association between adolescents' sleep time and a cardiometabolic risk score. A second aim was to examine associations between sleep time and individual cardiometabolic risk factors.
  
  
  METHODS
  Adolescents (N=699; ages, 12.5-17.5 years) participating in the HELENA (Healthy Lifestyle in Europe by Nutrition in Adolescence) study were examined. Sleep time was reported by a questionnaire. Physical activity (PA) was assessed by accelerometry (n=497). Cardiometabolic risk factors measurements included insulin resistance, blood pressure, adiposity markers, cardiorespiratory fitness, and blood lipids. A cardiovascular disease risk score was computed. Associations were examined by a multilevel regression analysis (linear for individual risk factors and Poisson for the clustered risk score).
  
  
  RESULTS
  For school days no association was found between sleep time and cardiometabolic risk factors. At weekend days, the prevalence ratio (PR) of having a clustered risk score increased by 15% for each additional hour of sleep controlling for age, sex, and socioeconomic status (SES); however, the prevalence disappeared when adjusting for PA.
  
  
  CONCLUSIONS
  In European adolescents sleep time is not associated with cardiometabolic risk factors when important confounders are considered. Future research about sleep cardiovascular risk factors should register other sleep dimensions (sleep patterns or disturbances) to provide a better insight in this scientific field.
authors.affiliation: School of Medicine of the University of São Paulo, Department of Preventive Medicine, São Paulo, Brazil; GENUD Research Group, University of Zaragoza, Spain. Electronic address: jprey@unizar.es.
authors.forename: J P
authors.initials: JP
authors.lastname: Rey-López
authors.affiliation: School of Medicine of the University of São Paulo, Department of Preventive Medicine, São Paulo, Brazil.
authors.forename: H B
authors.initials: HB
authors.lastname: de Carvalho
authors.affiliation: School of Medicine of the University of São Paulo, Department of Preventive Medicine, São Paulo, Brazil; GENUD Research Group, University of Zaragoza, Spain.
authors.forename: A C F
authors.initials: AC
authors.lastname: de Moraes
authors.affiliation: Department of Physical Education and Sport, Faculty of Sport Sciences, University of Granada, Granada, Spain; Department of Biosciences and Nutrition at NOVUM, Karolinska Institutet, Huddinge, Sweden.
authors.forename: J R
authors.initials: JR
authors.lastname: Ruiz
authors.affiliation: Department of Biosciences and Nutrition at NOVUM, Karolinska Institutet, Huddinge, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Sjöström
authors.affiliation: Immunonutrition Research Group, Department of Metabolism and Nutrition, Institute of Food Science and Technology and Nutrition (ICTAN), Spanish National Research Council (CSIC), Madrid, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Marcos
authors.affiliation: National Research Institute for Food and Nutrition, INRAN, Rome, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Polito
authors.affiliation: Pôle Enfant, Hôpital J de Flandre, CHRU de Lille Inserm U995, Faculté de Médecine, Université Lille 2, Lille, France.
authors.forename: F
authors.initials: F
authors.lastname: Gottrand
authors.affiliation: Department of Nutrition and Dietetics, Harokopio University, Athens, Greece.
authors.forename: Y
authors.initials: Y
authors.lastname: Manios
authors.affiliation: University of Crete School of Medicine, Department of Social Medicine, Preventive Medicine and Nutrition Clinic, Crete, Greece.
authors.forename: A
authors.initials: A
authors.lastname: Kafatos
authors.affiliation: Department of Paediatrics, University of Pecs, Pécs-József, Hungary.
authors.forename: D
authors.initials: D
authors.lastname: Molnar
authors.affiliation: Department of Pediatrics, Private Medical University, Salzburg, Austria.
authors.forename: K
authors.initials: K
authors.lastname: Widhalm
authors.affiliation: Department of Public Health, Faculty of Medicine and Health Sciences, Ghent University, Belgium.
authors.forename: S
authors.initials: S
authors.lastname: De Henauw
authors.affiliation: GENUD Research Group, University of Zaragoza, Spain.
authors.forename: L A
authors.initials: LA
authors.lastname: Moreno
mesh_terms: D061725:Accelerometry; D000293:Adolescent; D000294:Adolescent Behavior; D002318:Cardiovascular Diseases / Q000453:epidemiology*; D002648:Child; D015986:Confounding Factors, Epidemiologic; D003430:Cross-Sectional Studies; D005060:Europe / Q000453:epidemiology; D005260:Female; D006306:Health Surveys; D006801:Humans; D008019:Life Style; D008297:Male; D008659:Metabolic Diseases / Q000453:epidemiology*; D010809:Physical Fitness; D015995:Prevalence; D012044:Regression Analysis; D012307:Risk Factors; D012890:Sleep; D012893:Sleep Wake Disorders / Q000453:epidemiology*
keywords: Accelerometry; Cardiometabolic risk; Cardiorespiratory fitness; Multilevel analysis; Physical activity; Sleep duration