title: Reliability and validity of a screen time-based sedentary behaviour questionnaire for adolescents: The HELENA study.
abstract: BACKGROUND
  Although there is a growing interest in the epidemiology of sedentary behaviours, it is unknown whether sedentary behaviour questionnaires are broad markers of sedentary time. The aims of this study were to determine the: (i) reliability of the Healthy Lifestyle in Europe by Nutrition in Adolescence (HELENA) screen time-based sedentary behaviour questionnaire; and (ii) its validity, i.e. the ability of the questionnaire to correctly rank adolescents according to the objectively measured sedentary time.
  
  
  METHODS
  A total of 183 adolescents (104 females aged 12.5-17.5 years) were involved in the reliability study. Participants completed the HELENA sedentary questionnaire twice (1 week apart). The validity study comprised 2048 (1212 females) adolescents (12.5-17.5 years of age) included in the HELENA cross-sectional study. Questions included television viewing, computer games, console games, Internet for study and non-study reasons and study during week and weekend days. We compared median values of sedentary time, using accelerometers, by tertiles of self-reported sedentary behaviours and their sum (composite sedentary score).
  
  
  RESULTS
  Reliability study: κ-values showed a good agreement (>0.7), except for Internet for study reasons (0.46 weekdays, 0.33 weekend). The questionnaire correctly classified boys' sedentary time when analysed by specific behaviours and by a composite sedentary score. In girls, median values of objectively measured sedentary time were not different across tertiles of self-reported sedentary behaviours or the composite sedentary score.
  
  
  CONCLUSIONS
  The HELENA sedentary questionnaire is reliable, yet only correctly classifies objectively measured sedentary time in boys.
authors.affiliation: GENUD Research Group, Department of Physiotherapy and Nursing, University of Zaragoza, Spain. jprey@unizar.es
authors.forename: Juan P
authors.initials: JP
authors.lastname: Rey-López
authors.forename: Jonatan R
authors.initials: JR
authors.lastname: Ruiz
authors.forename: Francisco B
authors.initials: FB
authors.lastname: Ortega
authors.forename: Maite
authors.initials: M
authors.lastname: Verloigne
authors.forename: German
authors.initials: G
authors.lastname: Vicente-Rodriguez
authors.forename: Luis
authors.initials: L
authors.lastname: Gracia-Marco
authors.forename: Frederic
authors.initials: F
authors.lastname: Gottrand
authors.forename: Denes
authors.initials: D
authors.lastname: Molnar
authors.forename: Kurt
authors.initials: K
authors.lastname: Widhalm
authors.forename: Maria
authors.initials: M
authors.lastname: Zaccaria
authors.forename: Magdalena
authors.initials: M
authors.lastname: Cuenca-García
authors.forename: Michael
authors.initials: M
authors.lastname: Sjöström
authors.forename: Ilse
authors.initials: I
authors.lastname: De Bourdeaudhuij
authors.forename: Luis A
authors.initials: LA
authors.lastname: Moreno
mesh_terms: D000293:Adolescent; D003201:Computers; D015444:Exercise; D005260:Female; D015438:Health Behavior; D006306:Health Surveys / Q000592:standards / Q000706:statistics & numerical data*; D006801:Humans; D020407:Internet; D008019:Life Style; D008297:Male; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires; D013690:Television; D013997:Time Factors