title: Daily self-reports resulted in information bias when assessing exposure duration to computer use.
abstract: BACKGROUND
  Self-reported exposure duration to computer use is widely used in exposure assessment, and this study examined the associated information bias in a repeated measures setting.
  
  
  METHODS
  For 3 weeks, 30 undergraduate students reported daily cumulative computer-use duration and musculoskeletal symptoms at four random times per day. Usage-monitor software installed onto participant's personal computers provided the reference measure. We compared daily self-reported and software-recorded duration, and modeled the effect of musculoskeletal symptoms on observed differences.
  
  
  RESULTS
  The relationships between daily self-reported and software-recorded computer-use duration varied greatly across subject with Spearman's correlations ranging from -0.22 to 0.8. Self-reports generally overestimated computer use when software-recorded durations were less than 3.6 hr, and underestimated when above 3.6 hr. Experiencing symptoms was related to a 0.15-hr increase in self-reported duration after controlling for software-recorded duration.
  
  
  CONCLUSIONS
  Daily self-reported computer-use duration had a weak-to-moderate correlation with software-recorded duration, and their relationship changed slightly with musculoskeletal symptoms. Self-reports resulted in both non-differential and differential information bias.
authors.affiliation: Department of Environmental Health, Harvard University, Boston, Massachusetts, USA.
authors.forename: Che-Hsu Joe
authors.initials: CH
authors.lastname: Chang
authors.forename: Cammie Chaumont
authors.initials: CC
authors.lastname: Menéndez
authors.forename: Michelle M
authors.initials: MM
authors.lastname: Robertson
authors.forename: Benjamin C
authors.initials: BC
authors.lastname: Amick
authors.forename: Peter W
authors.initials: PW
authors.lastname: Johnson
authors.forename: Rosa J
authors.initials: RJ
authors.lastname: del Pino
authors.forename: Jack T
authors.initials: JT
authors.lastname: Dennerlein
mesh_terms: D000328:Adult; D015982:Bias; D003625:Data Collection / Q000379:methods / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D008838:Microcomputers; D016273:Occupational Exposure / Q000706:statistics & numerical data*; D057566:Self Report; D012984:Software; D018709:Statistics, Nonparametric; D013647:Task Performance and Analysis; D055815:Young Adult