title: Validity of self-report methods for measuring sedentary behaviour in older adults.
abstract: OBJECTIVE
  Sedentary behaviour (SB) is associated with a range of negative health outcomes, but little is known about the validity of self-report methods for measuring SB in older adults. Thus, the aim was to assess the reliability and validity of two instruments for measuring SB in older adults.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  41 community-dwelling older adults (14/27 male/female, 74.5 ± 7.6 years) wore an ActivPAL(3)™ (AP) for 7 consecutive days, then completed (1) a single question (SQ) to assess sitting time on a usual weekday, weekend day and yesterday (i.e. the last day of monitoring), and (2) a computer-delivered 24-h recall (MARCA) for the last two days. Intraclass correlation (ICC) and standard error of measurement (SEM) were used to assess test-retest reliability; validity was examined using Spearman's correlation, mean bias and limits of agreement, and kappa for classifying tertiles of time in SB, with AP as the reference standard.
  
  
  RESULTS
  For the SQ, the ICC ranged from 0.64 to 0.79, with SEM 1.03-1.42 h/day. ICC for the MARCA ranged from 0.72 to 0.96, with SEM 0.47-1.18 h/day. The SQ showed modest correlation with AP (r = 0.13-0.33), with mean biases of about -3.5 h/day. The MARCA showed moderate correlation with AP (r = 0.49-0.67), with mean biases of about 1.4 h/day. When categorised into tertiles, agreement was significant but fair for the SQ, and moderate for the MARCA.
  
  
  CONCLUSIONS
  Both measures have acceptable reliability, but the MARCA provides more valid estimates of SB than the SQ, which underestimates SB in this group of older adults.
authors.affiliation: The University of Queensland, School of Human Movement Studies, Australia; Universidad de La Frontera, Departamento de Educación Física Deportes y Recreación, Chile. Electronic address: nicolas.aguilar@ufrontera.cl.
authors.forename: Nicolás
authors.initials: N
authors.lastname: Aguilar-Farías
authors.affiliation: The University of Queensland, School of Human Movement Studies, Australia.
authors.forename: Wendy J
authors.initials: WJ
authors.lastname: Brown
authors.affiliation: The University of South Australia, Health and Use of Time (HUT) Group, Australia.
authors.forename: Timothy S
authors.initials: TS
authors.lastname: Olds
authors.affiliation: The University of Queensland, School of Human Movement Studies, Australia; The University of Queensland, School of Population Health, Australia.
authors.forename: G M E E
authors.initials: GM
authors.lastname: Geeske Peeters
mesh_terms: D056044:Actigraphy; D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D005260:Female; D015438:Health Behavior; D006801:Humans; D008297:Male; D009043:Motor Activity; D015203:Reproducibility of Results; D057185:Sedentary Behavior; D057566:Self Report
keywords: ActivPAL; MARCA; Questionnaires; Time use