Characterizing ActiGraph's idle sleep mode

Authors

• SR LaMunion
• RJ Brychta
• A Ishiharaa
• KY Chen

Abstract

Idle sleep mode (ISM) is an optional battery-conserving feature for ActiGraph accelerometers that may have implications for data handling when data are collected with ISM enabled. There is limited documentation of the properties and characteristics of ISM, however, it is generally believed to engage during nonwear, periods of inactivity, and sleep. Here we characterize the features of ISM using 1) a controlled experiment of one week of continuous, simultaneous wear of two ActiGraph wGT3X-BT devices, with and without ISM enabled, and 2) during a seven-day assessment in a nationally representative sample of 13,649 participants (6-80 y) in the United States. In the controlled experiment, we found ISM engaged 38.9% ± 3.0% of the day (Mean ± SD) during 411.1 ± 93.2 unique events∙day-1 with a 16.7 ± 3.5 second median duration. There were fewer (75.6 ± 14.0 events) but longer (117.2 ± 62.2 seconds) events in the early morning (00:00-05:59) and more frequent (146.4 ± 63.6 events) but shorter (9.7 ± 2.9 seconds) events in the afternoon (12:00-17:59). In the national sample, daily ISM engagement was (Mean ± SE) 43.6% ± 0.2% with the highest engagement during the early morning (78.4% ± 0.2%) and lowest during the afternoon (20.4% ± 0.3%). ISM engages during a substantial portion of the day, which is greater during, but not limited to, periods of low movement, such as plausible sleep or probable nonwear. Additional research is needed to better inform future study designs and analyses and interpretations of data previously collected with ISM enabled.

Scientific Focus Area: Epidemiology

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