Raw Accelerometer Data Analysis with GGIR R-package

PURPOSE: This study aimed to determine the agreement between outputs from contemporaneous measures of acceleration from wrist-worn GENEActiv and ActiGraph accelerometers when processed using the GGIR open source package. METHODS: Thirty-four participants wore a GENEActiv and an ActiGraph GT3X+ on their nondominant wrist continuously for 2 d to ensure the capture of one 24-h day and one nocturnal sleep. GENEActiv.bin files and ActiGraph .csv files were analyzed with R-package GGIR version 1.2-0. Key outcome variables were as follows: wear time, average magnitude of dynamic wrist acceleration (Euclidean norm minus one ENMO), percentile distribution of accelerations, time spent across acceleration levels in a 40-mg resolution, time in moderate-to-vigorous physical activity (MVPA: total, 10-min bouts), and duration of nocturnal sleep. RESULTS: There was a high agreement between accelerometer brands for all derived outcomes (wear time, MVPA, and sleep; intraclass correlation coefficient ICC > 0.96), ENMO (ICC = 0.99), time spent across acceleration levels (ICC > 0.93), and accelerations ≥50th percentile of the distribution (ICC > 0.82). ENMO (mean ± SD, GENEActiv = 29.9 ± 20.7 mg, ActiGraph = 27.8 ± 21.4 mg) and accelerations between the 5th and the 75th percentile of the distribution measured by the GENEActiv were significantly higher than those measured by the ActiGraph. Correspondingly, the number of minutes recorded between 0 and 40 mg was significantly greater for the ActiGraph (745 min cf. 734 min), and the number of minutes recorded between 40 and 80 mg was significantly greater for the GENEActiv (110 min cf. 105 min). CONCLUSION: Derived outcomes (wear time, MVPA, and sleep) were similar between brands. Brands compared well for acceleration magnitudes >50-80 mg but not lower magnitudes indicative of sedentary time. Caution is advised when comparing the magnitude of ENMO between brands, but there was a high consistency between brands for the ranking of individuals for activity and sleep outcomes.