Raw Accelerometer Data Analysis with GGIR R-package: Does Accelerometer Brand Matter?

PURPOSE: 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 ActiGraph GT3X+ on their non-dominant wrist continuously for two days to ensure capture of one 24 h day and one nocturnal sleep. GENEActiv.bin files and ActiGraph.csv files were analysed with R-package GGIR version 1.2-0. Key outcome variables were: wear time, average magnitude of dynamic wrist acceleration (ENMO), percentile distribution of accelerations, time spent across acceleration levels in 40 mg resolution, time in moderate-to-vigorous physical activity (MVPA: total, 10-min bouts) and duration of nocturnal sleep. RESULTS: There was high agreement between accelerometer brands for all derived outcomes (wear time, MVPA and sleep, 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 (GENEActiv = 29.9±20.7(SD)) mg, ActiGraph = 27.8±21.4 mg) and accelerations between the 5th and 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 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 high consistency between brands for the ranking of individuals for activity and sleep outcomes.