Objective measurement of sedentary behavior: impact of non-wear time rules on changes in sedentary time

Abstract

BackgroundAccelerometry non-wear time rules might affect sedentary time, and the associations with health outcomes such as adiposity. However, the exact effect of different non-wear time rules on sedentary time and reported changes in sedentary time is unknown. This study evaluated the effect of different accelerometry non-wear time rules on sedentary time and changes in sedentary time from age 9–12 years.MethodsAccelerometry data were collected as part of the Gateshead Millennium Birth Cohort study. Participants were 9.3 (±0.4) years at baseline (n = 517) and 12.5 (±0.3) years at follow-up (n = 440). Sedentary time was defined using an accelerometry cut-point of 25 counts per 15 s. Non-wear time was defined using manual data reduction (the reference method) and 10 min, 20 min and 60 min consecutive zeros. Differences between methods were analyzed using repeated measures ANOVA with Bonferroni post-hoc analyses.ResultsMean daily sedentary time at age 9 ranged from 364 min per day to 426 min using the 10 min and 60 min rule, respectively (p < 0.05). At 12 years, mean daily sedentary times ranged from 424 min to 518 min (p < 0.05). Mean changes in daily sedentary time over the three years ranged from 60 min to 93 min using the 10 min and 60 min rule, respectively (p < 0.05). When adjusting for wear time, differences in average sedentary time between methods decreased from 62 min to 27 min (age 9), 95 min to 32 min (age 12) and 33 min to 10 min (changes between 9 to 12 years).ConclusionsUsing different non-wear time rules results in significant differences in daily sedentary time and changes in sedentary time. Correcting for wear time appears to be a reasonable approach to limiting these differences and may improve comparability between future studies. Using the 20 min rule, while correcting for wear time, provided the most accurate estimates of sedentary time and changes in sedentary time, compared to the manual reference in 9–12 year-olds.

Impact of an 8-Month Trial Using Height-Adjustable Desks on Children’s Classroom Sitting Patterns and Markers of Cardio-Metabolic and Musculoskeletal Health

“…Non-wear time was defined as 20 min of consecutive zero counts, for both devices [47]. In the activPAL this was determined from the accelerometer rather than postural data.…”

Clinical impact of sedentary behaviors in adult survivors of acute lymphoblastic leukemia: A report from the St. Jude Lifetime Cohort study

“…Finally, the difference between the 2 groups was small (approximately 2%), and is likely not clinically significant; survivors are as sedentary as their peers. Although survivors and controls wore their accelerometers on average for >7 days, which is adequate to capture usual activity, accelerometers do not provide the opportunity to determine posture or prolonged sedentary time . In addition, we used 60‐second epochs to capture activity.…”

“…Although survivors and controls wore their accelerometers on average for >7 days, which is adequate to capture usual activity, 20 accelerometers do not provide the opportunity to determine posture or prolonged sedentary time. 21 In addition, we used 60-second epochs to capture activity. Other programmed intervals may be more appropriate.…”

Development and feasibility testing of an intervention to support active lifestyles in youths with type 1 diabetes—the ActivPals programme: a study protocol

“…Accelerometer data will be downloaded to Actilife software (version 6.4.3). In line with previous studies, a minimum wear time for a valid day will be defined as 6 h/day, with 3 days of data required for analysis inclusion [33, 34]. …”