1. Measuring Sedentary Behavior: Epoch- and Hour-level
Agreement between the ActiGraph and activPAL
Jonathan Finch, BA1, Tarrah B. Mitchell, MA2, Kelsey B. Borner, MA2, Jordan Carlson, PhD1
1Center for Healthy Lifestyles and Nutrition, Kansas City, MO; 2University of Kansas, Lawrence, KS
Background
For children and adults, 55-70% of daily activity is spent sedentary
High percentages are concerning due to a myriad of negative physical and psychosocial health outcomes associated with sedentary behavior
ActiGraph cut-point methods are commonly used for measuring physical activity and sedentary behavior, but the ActiGraph measures acceleration and may not be an appropriate method for measuring sitting, which involves a postural component
On the other hand, the activPAL is considered the gold standard for measuring sedentary behavior
The goal was to investigate the validity of ActiGraph cut-points for assessing sedentary behavior by examining the agreement between the activPAL and the ActiGraph in youth and adult samples
Methods
9 children (ages 10-17) and 12 adults (ages 25-63) participated for 1 day
Participants wore three devices that measured sitting and standing
Waist-worn ActiGraph (GT3X; processed in regular frequency and low-frequency [LF]) – test device
Wrist-worn ActiGraph (GT3X) – test device
Thigh-worn activPAL (Micro) – gold-standard comparison
Collected in 15-second epochs and summarized into 1-hour intervals
Variables of interest:
Total sitting time, calculated as the per cent of the hour spent sitting
Number of sit-to-stand transitions, calculated as the number of times the participant went from sitting to standing (activPAL) or from <25 to ≥25 counts per 15-second epoch (ActiGraph)
Confusion matrices were used to calculate agreement at epoch-level, and mixed-effects linear regression was used to estimate mean differences at hour-level
Table 1: Epoch-level agreement in adult sample (N = XX epochs)
Total Sedentary Time
Sit-to-Stand Transitions
Accuracy
Sensitivity
Specificity
Waist ActiGraph
89.54%
97.28%
35.03%
96.48%
56.53%
97.47%
Waist-LF ActiGraph
89.10%
96.42%
37.53%
96.08%
57.10%
97.04%
Wrist ActiGraph
62.92%
61.74%
70.88%
83.93%
32.27%
85.32%
Table 2: Epoch-level agreement in youth sample (N=XXX epochs)
Total Sedentary Time
Sit-to-Stand Transitions
Accuracy
Sensitivity
Specificity
Waist ActiGraph
65.90%
86.68%
57.44%
87.67%
31.07%
90.09%
Waist-LF ActiGraph
68.99%
82.01%
63.68%
88.23%
90.67%
Wrist ActiGraph
73.76%
28.30%
92.28%
90.06%
10.68%
93.45%
Adult Analyses (N = xx hours):
Youth Analyses (N = xx hours):
Figure 1. Percent of hour spent sedentary
Figure 3. Percent of hour spent sedentary
Conclusions
The 100 counts-per-minute cut point for the wrist ActiGraph does not appear to provide a valid measure of either total sedentary time or sit-to-stand transitions, which is not surprising because the wrist position captures arm movement that is often independent of posture.
The100 counts-per-minute cut-point for the waist ActiGraph appears to have validity for assessing total sedentary time. However, this cut-point does not appear to have acceptable validity for assessing sit-to-stand transitions
The Waist and Waist-LF ActiGraph performed similarly
Validity was better in the adult sample than the youth sample.
More research is needed to understand how this level of measurement error impacts the scoring of daily bout patterns and associations with health outcomes
Figure 2. Number of sit-stand transitions per hour
Figure 4. Number of sit-stand transitions per hour
This poster was presented at the National Conference in Clinical Child and Adolescent Psychology (September 2016) in Lawrence, KS. For more information about this project, please contact Jordan Carlson at