Effects of ActiGraph's filter, epoch length and non-wearing time algorithm on step counts in people with COPD

• Published in: Journal of sports sciences Vol. 42; no. 1; pp. 9 - 16
• Main Authors: Antão, Joana, Rebelo, Patrícia, Almeida, Sara, Franssen, Frits M. E., Spruit, Martijn A., Marques, Alda
• Format: Journal Article
• Language: English
• Published: England Routledge 2024; Taylor & Francis Ltd
• Subjects: accelerometry; Algorithms; Chronic obstructive pulmonary disease; Filters; Lung diseases; physical activity; Pulmonary disease, chronic obstructive; accelerometry; Pulmonary disease, chronic obstructive; physical activity
• ISSN: 0264-0414; 1466-447X; 1466-447X
• DOI: 10.1080/02640414.2024.2319448

The influence of the ActiGraph® processing criteria on estimating step counts in chronic obstructive pulmonary disease (COPD) remains uncertain. This study aimed to assess the influence of filters, epoch lengths and non-wearing time (NWT) algorithms on steps/day in people with COPD. ActiGraph GT3X+ was worn on the waist for seven days. Steps were detected using different filters (normal and low-frequency extension [LFE]), epoch lengths (15s and 60s), and NWT algorithms (Choi and Troiano). Linear mixed-effects model was applied to assess the effects of filter, epoch length, NWT algorithm on steps/day. Lin's concordance correlation and Bland-Altman were used to measure agreement. A total of 136 people with COPD (107 male; 69 ± 8 years; FEV 1 51 ± 17% predicted) were included. Significant differences were found between filters (p < 0.001), but not between epoch lengths or NWT algorithms. The LFE increased, on average, approximately 7500 steps/day compared to the normal filter (p < 0.001). Agreement was poor (<0.3) and proportional bias was significant when comparing steps/day computed with different filters, regardless of the epoch length and NWT algorithm. Filter choice but not epoch lengths or NWT algorithms seem to impact measurement of steps/day. Future studies are needed to recommend the most accurate technique for measuring steps/day in people with COPD.