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.
Design: Cross-sectional study.
Methods: 41 community-dwelling older adults (14/27 male/female, 74.5±7.6 years) wore an ActivPAL3™ (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.
Conclusion: 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.