Measurement of sedentary time and physical activity in rheumatoid arthritis: an ActiGraph and activPAL™ validation study

• Published in: Rheumatology international Vol. 40; no. 9; pp. 1509 - 1518
• Main Authors: O’Brien, Ciara M., Duda, Joan L., Kitas, George D., Veldhuijzen van Zanten, Jet J. C. S., Metsios, George S., Fenton, Sally A. M.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-09-2020; Springer Nature B.V
• Subjects: Actigraphy - instrumentation; Actigraphy - standards; Adult; Aged; Arthritis, Rheumatoid - physiopathology; Exercise; Female; Humans; Laboratories; Male; Medicine; Medicine & Public Health; Middle Aged; Rheumatoid arthritis; Rheumatology; Sedentary Behavior; Validation Studies; Activity trackers; Physical activity; Sedentary behaviour; Rheumatoid arthritis
• ISSN: 0172-8172; 1437-160X
• DOI: 10.1007/s00296-020-04608-2

Accurate measurement of sedentary time and physical activity (PA) is essential to establish their relationships with rheumatoid arthritis (RA) outcomes. Study objectives were to: (1) validate the GT3X+ and activPAL3
μ
™, and develop RA-specific accelerometer (count-based) cut-points for measuring sedentary time, light-intensity PA and moderate-intensity PA (laboratory-validation); (2) determine the accuracy of the RA-specific (vs. non-RA) cut-points, for estimating free-living sedentary time in RA (field-validation).
Laboratory-validation
: RA patients (
n
 = 22) were fitted with a GT3X+, activPAL3
μ
™ and indirect calorimeter. Whilst being video-recorded, participants undertook 11 activities, comprising sedentary, light-intensity and moderate-intensity behaviours. Criterion standards for devices were indirect calorimetry (GT3X+) and direct observation (activPAL3
μ
™).
Field-validation
: RA patients (
n
 = 100) wore a GT3X+ and activPAL3
μ
™ for 7 days. The criterion standard for sedentary time cut-points (RA-specific vs. non-RA) was the activPAL3
μ
™. Results of the laboratory-validation: GT3X—receiver operating characteristic curves generated RA-specific cut-points (counts/min) for: sedentary time = ≤ 244; light-intensity PA = 245–2501; moderate-intensity PA ≥ 2502 (all sensitivity ≥ 0.87 and 1-specificity ≤ 0.11). ActivPAL3
μ
™—Bland–Altman 95% limits of agreement (lower–upper [min]) were: sedentary = (− 0.1 to 0.2); standing = (− 0.7 to 1.1); stepping = (− 1.2 to 0.6). Results of the field-validation: compared to the activPAL3
μ
™, Bland–Altman 95% limits of agreement (lower–upper) for sedentary time (min/day) estimated by the RA-specific cut-point = (− 42.6 to 318.0) vs. the non-RA cut-point = (− 19.6 to 432.0). In conclusion, the activPAL3
μ
™ accurately quantifies sedentary, standing and stepping time in RA. The RA-specific cut-points offer a validated measure of sedentary time, light-intensity PA and moderate-intensity PA in these patients, and demonstrated superior accuracy for estimating free-living sedentary time, compared to non-RA cut-points.