Validation of Accelerometer Wear and Nonwear Time Classification Algorithm

Department of Biostatistics, Vanderbilt University School of Medicine, Nashville, TN 37232-2260, USA.
Medicine and science in sports and exercise (Impact Factor: 3.98). 02/2011; 43(2):357-64. DOI: 10.1249/MSS.0b013e3181ed61a3
Source: PubMed


the use of movement monitors (accelerometers) for measuring physical activity (PA) in intervention and population-based studies is becoming a standard methodology for the objective measurement of sedentary and active behaviors and for the validation of subjective PA self-reports. A vital step in PA measurement is the classification of daily time into accelerometer wear and nonwear intervals using its recordings (counts) and an accelerometer-specific algorithm.
the purpose of this study was to validate and improve a commonly used algorithm for classifying accelerometer wear and nonwear time intervals using objective movement data obtained in the whole-room indirect calorimeter.
we conducted a validation study of a wear or nonwear automatic algorithm using data obtained from 49 adults and 76 youth wearing accelerometers during a strictly monitored 24-h stay in a room calorimeter. The accelerometer wear and nonwear time classified by the algorithm was compared with actual wearing time. Potential improvements to the algorithm were examined using the minimum classification error as an optimization target.
the recommended elements in the new algorithm are as follows: 1) zero-count threshold during a nonwear time interval, 2) 90-min time window for consecutive zero or nonzero counts, and 3) allowance of 2-min interval of nonzero counts with the upstream or downstream 30-min consecutive zero-count window for detection of artifactual movements. Compared with the true wearing status, improvements to the algorithm decreased nonwear time misclassification during the waking and the 24-h periods (all P values < 0.001).
the accelerometer wear or nonwear time algorithm improvements may lead to more accurate estimation of time spent in sedentary and active behaviors.

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    • "With a specific software (ActiLife, version 6.9, Actigraph, Florida), data was reduced into one-minute periods (epochs), organized into daily physical activity and analyzed after data collection . Wear and nonwear time was determined according to Choi et al. (2011) algorithm. Time periods with at least 10 consecutive minutes of zero counts recorded were excluded from analysis assuming that the monitor was not worn. "
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    ABSTRACT: Unlabelled: Nonalcoholic fatty liver disease (NAFLD) is one of the most frequent complications associated with excess adiposity and has been identified as the leading cause of liver disease in pediatric populations worldwide. Because cardiorespiratory fitness (CRF) is related to physical activity (PA) levels, and increased PA plays a protective role against NAFLD risk factors, the aim of this study was to analyze the association between PA and a fatty liver marker (alanine aminotransferase - ALT) in obese children and adolescents, independently of central adiposity or CRF. 131 obese children (83 girls, 7-15 year-olds) involved in a PA promotion program comprised the sample. Measurements included anthropometric and body composition evaluations (DEXA), biological measurements (venipuncture), CRF (progressive treadmill test), PA (accelerometry), and maturational stage (Tanner criteria). The associations between ALT with PA intensities, central obesity, and CRF were calculated by three different models of linear regression, adjusted for potential confounders. Level of significance was set at 95%. Results: ALT was negatively associated with MVPA (β = -0.305), and CRF (β = -0.426), and positively associated with central obesity (β=.468). After adjustment for central obesity the negative and statistically significant association between ALT with MVPA (β = -0.364) and CRF (β = -0.550) still persists while a positive and significantly correlation was shown between ALT and SB (β = 0.382). Additional adjustment for CRF (Model 3) showed significant associations for all the PA intensities analyzed including light activity. PA at different intensities is associated to a fatty liver marker in obese children and adolescents, independently of central adiposity or CRF. Key pointsIn a previous study our group observed that there might be a potential protective effect of cardiorespiratory fitness (CRF) against abnormal ALT values;Considering that CRF is related to physical activity (PA), and increased PA plays a protective role against fatty liver, we hypothesized that it might be an association between PA and fatty liver in obese youth, independently of central adiposity or CRF;No other study has investigated these associations in obese youth;Our findings stresses the fact that moderate-to-vigorous and light physical activities, as well as lower sedentary behavior, is associated with lower fatty liver marker, independent of the effect of potential mediators, such as central obesity or CRF.
    Journal of sports science & medicine; 03/2015
    • "Participants wore the accelerometer on seven consecutive days (Monday to Sunday) and a minimum wear time of 10 h per day was considered valid data for the analysis (Rich et al., 2013). Non-wear time was defined as a period of at least 60 consecutive minutes of zero counts (Byun et al., 2011; Choi et al., 2011; Pfeiffer et al., 2009). In this study, the epoch duration was set to 5 s, which has been shown to be more accurate for the assessment of the spontaneous and intermittent activities of the young children (Vale et al., 2009). "
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    ABSTRACT: Public health organizations recommend that preschool-aged children accumulate at least 3h of physical activity (PA) daily. Objective monitoring using pedometers offers an opportunity to measure preschooler's PA and assess compliance with this recommendation. The purpose of this study was to derive step-based recommendations consistent with the 3h PA recommendation for preschool-aged children. The study sample comprised 916 preschool-aged children, aged 3 to 6years (mean age=5.0±0.8years). Children were recruited from kindergartens located in Portugal, between 2009 and 2013. Children wore an ActiGraph GT1M accelerometer that measured PA intensity and steps per day simultaneously over a 7-day monitoring period. Receiver operating characteristic (ROC) curve analysis was used to identify the daily step count threshold associated with meeting the daily 3hour PA recommendation. A significant correlation was observed between minutes of total PA and steps per day (r=0.76, p<0.001). The optimal step count for ≥3h of total PA was 9099 steps per day (sensitivity (90%) and specificity (66%)) with area under the ROC curve=0.86 (95% CI: 0.84 to 0.88). Preschool-aged children who accumulate less than 9000 steps per day may be considered insufficiently active. Copyright © 2014. Published by Elsevier Inc.
    Preventive Medicine 11/2014; 70. DOI:10.1016/j.ypmed.2014.11.008 · 3.09 Impact Factor
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    • "Participants were asked to wear the monitor on their right hip during all waking hours for 7 consecutive days. The number of MVPA minutes in bouts of 10 minutes or longer was computed by an algorithm by Choi et al. [19], while nonwear time was defined as 60 consecutive minutes with no counts, allowing for 2-minute interruptions with nonzero counts [20]. Bouts and wear-time were computed using the PhysicalActivity and Accelerometry R-packages. "
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    ABSTRACT: Roux-en-Y Gastric Bypass (RYGB) surgery among women often greatly decreases their body size. It may also change their spouses', children's, and their own physical activity (PA) and sedentary behavior (SB) patterns. The aim was objectively to measure and compare pre- to postsurgery changes in different PA intensities and SB in children and spouses 3 months before and 9 months after maternal RYGB. Recruitment from RYGB waiting lists at 5 Swedish hospitals generated a study population of 56 women, with 75 children aged 7-14 years, and 33 spouses. PA was measured over one week using tri-axial Actigraph GT3 X+accelerometers, and anthropometric measures were taken at home visits 3 months before and 9 months after maternal surgery. Mean time spent on moderate to vigorous PA (MVPA) by children pre- and postsurgery was 76.3 (SD 40.6) and 65.3 (SD 31.5) min/d, respectively, by spouses 31.2 (SD 18.0) and 33.6 (SD 18.1), and by the women 32.9 (SD 23.4.0) and 34.3 (SD 28.6). Mean time spent sedentary by children pre- and postsurgery was 320.7 (SD 143.4) and 374.4 (SD 123.3) min/d, respectively, by spouses 423.7 (SD 141.5) and 472.1 (SD 145.9), and by the women 425.5 (SD 138.2) and 420.0 (SD 127.8). Between 3 months before and 9 months after RYGB, objective measurements showed a significant decrease in MVPA and an increase in SB among children, but no differences were observed for spouses or women. Interventions may be needed to promote PA within the family after mothers' RYGB surgery. Copyright © 2015 American Society for Bariatric Surgery. Published by Elsevier Inc. All rights reserved.
    Surgery for Obesity and Related Diseases 10/2014; 11(3). DOI:10.1016/j.soard.2014.10.018 · 4.07 Impact Factor
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