Sitting time and changes in sitting time in children and adolescents: Impact of accelerometer data reduction decisions

Abstract

Introduction Accelerometer data reduction rules might affect sitting time. However, the impact of different data reduction decisions on sitting time remains uncertain. This study evaluated the effect of different non-wear time rules on sitting time and changes in sitting time from age 9 to 12 years. Methods Longitudinal ActiGraph accelerometry data were collected when participants were 9.3 (± 0.4) and 12.5 (± 0.3) years. Sitting time was defined using an accelerometer cutpoint of 25 counts/15 s. Non-wear time was defined using manual data reduction (the reference method) as well as rules using 10 min, 20 min and 60 min consecutive zeros. Differences between rules were analyzed using repeated measures Anova with Bonferoni post-hoc analyses. Results At age 9, sitting time between the 10 min and 60 min rules ranged from 364 min to 426 min per day depending (P Conclusion Using different data reduction rules results in significant differences in both sitting time and changes in sitting time in children and adolescents. Compared to the reference method, using the 20 min zero-string rule, while correcting for wear time, provided the most accurate estimates of sitting time and changes in sitting time in 9 to 12 year olds.