Equivalency of sleep estimates: comparison of three research-grade accelerometers


This study examined equivalency of sleep estimates from Axivity, GENEActiv and ActiGraph accelerometers worn on non-dominant and dominant wrist, and with and without using a sleep log to guide the algorithm.


Forty-seven young adults wore an Axivity, GENEActiv and ActiGraph accelerometer continuously on both wrists for 4-7 seven days. Sleep time, sleep window, sleep efficiency, sleep onset and wake time were produced using the open-source GGIR package. For each outcome, agreement between accelerometer brands, dominant and non-dominant wrists, and with and without a sleep log, was examined using pairwise 95% equivalence tests (±10% equivalence zone), intra-class correlation coefficients (ICCs) with 95% confidence intervals and limits of agreement (LoA).


All sleep outcomes were within a 10% equivalence zone

irrespective of brand, wrist, or use of a sleep log. ICCs were poor-to-good for sleep time

(ICCs>0.66) and sleep window (ICCs>0.56). Most ICCs were good-to-excellent for sleep

efficiency (ICCs>0.73), sleep onset (ICCs>0.88) and wake time (ICCs>0.87). There were

low levels of mean bias, however wide 95% LoA for sleep time, sleep window, sleep onset

and wake time outcomes. Sleep time (up to 25 min) and sleep window (up to 29 min) were

higher when sleep log was not used. Conclusion: The present findings suggest that sleep

outcomes from the Axivity, GENEActiv and ActiGraph, when analysed identically, are

comparable across studies with different accelerometer brands and wear protocols at a group

level. However, caution is advised when comparing studies that differ on sleep log