Utility of accelerometer thresholds for classifying sitting in office workers

• Published in: Preventive medicine Vol. 51; no. 5; pp. 357 - 360
• Main Authors: Oliver, Melody, Schofield, Grant M, Badland, Hannah M, Shepherd, Janine
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-11-2010
• Subjects: Acceleration; Actical; Activities of Daily Living; ActivPAL; Adult; Auckland; Candidates; Classification; Female; Humans; Internal Medicine; Male; Measure; Middle Aged; Monitoring, Ambulatory - instrumentation; Motor Activity; New Zealand; Office workers; Physical activity; Posture; Quantification; ROC Curve; Sedentary Lifestyle; Thresholds; Walking; Workplace; New Zealand; Measure; Sedentary lifestyle; ActivPAL; Adult; Physical activity; Actical
• ISSN: 0091-7435; 1096-0260
• DOI: 10.1016/j.ypmed.2010.08.010

Abstract Objective To investigate the utility of a variety of Actical accelerometer count thresholds for determining sitting time in a sample of office workers. Methods Data were collected from 21 participants in Auckland, New Zealand, between December 2009 and January 2010. Participants wore a hip-mounted Actical accelerometer and thigh-mounted activPAL inclinometer (criterion) for a 48-h period. Raw inclinometer and accelerometer data for each 15 s epoch of wear time were matched by date and time. Candidate accelerometer count thresholds for sitting classification were compared with the criterion measure using receiver operating characteristic analyses. Agreement in sitting time classification was determined using Bland–Altman methodology. Results Significant differences in area under the curve (AUC) values by threshold criteria were found ( p < 0.001). A threshold of 0 counts provided the highest combined sensitivity and specificity (AUC 0.759, 95%CI 0.756, 0.761). The 95% limits of agreement for time spent sitting were wide, at 328 min (range − 30.8, 297.5). Conclusion A threshold of 0 counts/15 s epoch with Actical accelerometers is likely to yield the most accurate quantification of sitting in office-based workers, however the wide limits of agreement found indicate limited utility of this threshold to accurately distinguish sitting time in office-based workers.