title: Is questionnaire-based sitting time inaccurate and can it be improved? A cross-sectional investigation using accelerometer-based sitting time.
abstract: To investigate the differences between a questionnaire-based and accelerometer-based sitting time, and develop a model for improving the accuracy of questionnaire-based sitting time for predicting accelerometer-based sitting time.
  
  
  
  183 workers in a cross-sectional study reported sitting time per day using a single question during the measurement period, and wore 2 Actigraph GT3X+ accelerometers on the thigh and trunk for 1-4 working days to determine their actual sitting time per day using the validated Acti4 software. Least squares regression models were fitted with questionnaire-based siting time and other self-reported predictors to predict accelerometer-based sitting time.
  
  
  
  Questionnaire-based and accelerometer-based average sitting times were ≈272 and ≈476 min/day, respectively. A low Pearson correlation (r=0.32), high mean bias (204.1 min) and wide limits of agreement (549.8 to -139.7 min) between questionnaire-based and accelerometer-based sitting time were found. The prediction model based on questionnaire-based sitting explained 10% of the variance in accelerometer-based sitting time. Inclusion of 9 self-reported predictors in the model increased the explained variance to 41%, with 10% optimism using a resampling bootstrap validation. Based on a split validation analysis, the developed prediction model on ≈75% of the workers (n=132) reduced the mean and the SD of the difference between questionnaire-based and accelerometer-based sitting time by 64% and 42%, respectively, in the remaining 25% of the workers.
  
  
  
  This study indicates that questionnaire-based sitting time has low validity and that a prediction model can be one solution to materially improve the precision of questionnaire-based sitting time.
authors.affiliation: National Research Centre for the Working Environment, Copenhagen, Denmark.
authors.forename: Nidhi
authors.initials: N
authors.lastname: Gupta
authors.affiliation: National Research Centre for the Working Environment, Copenhagen, Denmark.
authors.forename: Caroline Stordal
authors.initials: CS
authors.lastname: Christiansen
authors.affiliation: Federal Institute for Occupational Safety and Health (BAuA), Nöldnerstr, Berlin, Germany.
authors.forename: Christiana
authors.initials: C
authors.lastname: Hanisch
authors.affiliation: National Research Centre for the Working Environment, Copenhagen, Denmark.
authors.forename: Hans
authors.initials: H
authors.lastname: Bay
authors.affiliation: Federal Institute for Occupational Safety and Health (BAuA), Nöldnerstr, Berlin, Germany.
authors.forename: Hermann
authors.initials: H
authors.lastname: Burr
authors.affiliation: National Research Centre for the Working Environment, Copenhagen, Denmark.|Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark.
authors.forename: Andreas
authors.initials: A
authors.lastname: Holtermann
mesh_terms: D061725:Accelerometry / Q000379:methods*; D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D003718:Denmark; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011187:Posture; D015203:Reproducibility of Results; D057185:Sedentary Behavior; D057566:Self Report; D011795:Surveys and Questionnaires / Q000592:standards*; D013995:Time; D055815:Young Adult
keywords: EPIDEMIOLOGY; OCCUPATIONAL & INDUSTRIAL MEDICINE; PUBLIC HEALTH