Abstract
Until recently, methods for objective quantification of sitting time have been lacking.
The aim of this study was to validate self-reported measures against objectively measured
total sitting time and longest continuous time with uninterrupted sitting during working
hours, leisure time on workdays and leisuredays. Objective diurnal measurement of
sitting time was obtained among 26 office workers with 2 accelerometers (ActiGraph
GT3X+) for a 7-day period. Customized software (Acti4) was used to identify sitting
time separated from other sedentary behaviours. Self-reported sitting time was obtained
from a retrospective 7-day questionnaire. A generalized linear model showed the difference
between the methods. No significant correlations were found between objective and
self-reported sitting time (r<0.315). Total sitting time was significantly underestimated
(2.4 h) on a leisureday (p<0.001) and uninterrupted sitting time was in all 3 time
settings significantly overestimated (0.4–0.5 h) (p<0.045). Poor agreement (mean difference
between 0.5 to −2.4 h) between objectively measured and self-reported sitting time
was shown in Bland-Altman plots with wide (3.3–10.8 h) limits of agreement. This study
showed a great individual variation and a general lack of agreement between self-reported
vs. objectively measured total and uninterrupted sitting time. Objective measures
are recommended for determining sitting time.
Key words
objective physical activity measurements - sedentary behaviour - validity - ActiGraph
GT3X +
