Identifying accelerometer nonwear and wear time in older adults

Brent Hutto,Virginia J Howard,David Rhodes,John E Vena,Natalie Colabianchi,Steven P Hooker,Steven N Blair

doi:10.1186/1479-5868-10-120

Abstract

BackgroundFive accelerometer-derived methods of identifying nonwear and wear time were compared with a self-report criterion in adults ≥ 56 years of age.MethodsTwo hundred participants who reported wearing an Actical™ activity monitor for four to seven consecutive days and provided complete daily log sheet data (i.e., the criterion) were included. Four variables were obtained from log sheets: 1) dates the device was worn; 2) time(s) the participant put the device on each day; 3) time(s) the participant removed the device each day; and 4) duration of self-reported nonwear each day. Estimates of wear and nonwear time using 60, 90, 120, 150 and 180 minutes of consecutive zeroes were compared to estimates derived from log sheets.ResultsCompared with the log sheet, mean daily wear time varied from -84, -43, -24, -14 and -8 min/day for the 60-min, 90-min, 120-min, 150-min and 180-min algorithms, respectively. Daily log sheets indicated 8.5 nonwear bouts per week with 120-min, 150-min and 180-min algorithms estimating 8.2-8.9 nonwear bouts per week. The 60-min and 90-min methods substantially overestimated number of nonwear bouts per week and underestimated time spent in sedentary behavior. Sensitivity (number of compliant days correctly identified as compliant) improved with increasing minutes of consecutive zero counts and stabilized at the 120-min algorithm. The proportion of wear time being sedentary and absolute and proportion of time spent in physical activity of varying intensities were nearly identical for each method.ConclusionsUtilization of at least 120 minutes of consecutive zero counts will provide dependable population-based estimates of wear and nonwear time, and time spent being sedentary and active in older adults wearing the Actical™ activity monitor.

Highlights

Five accelerometer-derived methods of identifying nonwear and wear time were compared with a self-report criterion in adults ≥ 56 years of age
Several studies have been conducted to develop algorithms and activity count cut-points to aid in the differentiation between light, moderate and vigorous intensity physical activity in
A focus on time spent being sedentary has emerged with evidence indicating that sedentary behavior is significantly associated with several health-related factors independent of physical activity level [12,13]

Summary

Introduction

Five accelerometer-derived methods of identifying nonwear and wear time were compared with a self-report criterion in adults ≥ 56 years of age. The utilization of accelerometers to objectively monitor physical activity-related movement has become widespread over the past 15 years. Despite some limitations, these devices are well-suited to capture data associated with the most common form of locomotion in adults ≥ 50 years of age, namely walking. In a 2005 study, a participant was considered not to be wearing the device if 20 consecutive minutes of zero activity counts were recorded [16] This method was later modified with a commonly applied wear-time estimation algorithm using a string of 60 consecutive zeros, sometimes with minor allowances for interruptions to denote nonwear [8,17]. To avoid large underestimates of wear time, these comparison studies have recommended longer strings of zeroes (e.g., 90-120 minutes) than were commonly employed in the past [15,18,19,20,21,22]

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