1. Classification of Free-Living Body Posture with ECG Patch Accelerometers: Application to the Multicenter AIDS Cohort Study.
- Author
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Etzkorn LH, Heravi AS, Knuth ND, Wu KC, Post WS, Urbanek JK, and Crainiceanu CM
- Abstract
Purpose: As health studies increasingly monitor free-living heart performance via ECG patches with accelerometers, researchers will seek to investigate cardio-electrical responses to physical activity and sedentary behavior, increasing demand for fast, scalable methods to process accelerometer data. We extend a posture classification algorithm for accelerometers in ECG patches when researchers do not have ground-truth labels or other reference measurements (i.e., upright measurement)., Methods: Men living with and without HIV in the Multicenter AIDS Cohort study wore the Zio XT
® for up to two weeks (n = 1,250). Our novel extensions for posture classification include (1) estimation of an upright posture for each individual without a reference upright measurement; (2) correction of the upright estimate for device removal and re-positioning using novel spherical change-point detection; and (3) classification of upright and recumbent periods using a clustering and voting process rather than a simple inclination threshold used in other algorithms. As no posture labels exist in the free-living environment, we perform numerous sensitivity analyses and evaluate the algorithm against labelled data from the Towson Accelerometer Study, where participants wore accelerometers at the waist., Results: On average, 87.1% of participants were recumbent at 4am and 15.5% were recumbent at 1pm. Participants were recumbent 54 minutes longer on weekends compared to weekdays. Performance was good in comparison to labelled data in a separate, controlled setting (accuracy = 96.0%, sensitivity = 97.5%, specificity = 95.9%)., Conclusions: Posture may be classified in the free-living environment from accelerometers in ECG patches even without measuring a standard upright position. Furthermore, algorithms that fail to account for individuals who rotate and re-attach the accelerometer may fail in the free-living environment., Competing Interests: Competing Interests The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. Drs. Etzkorn, Heravi, Knuth, Wu, and Post report no conflicts of interest with the present work. Dr. Ciprian Crainiceanu is consulting for Bayer, Johnson and Johnson, and Cytel on methods development for wearable and implantable technologies. The details of these contracts are disclosed through the Johns Hopkins University eDisclose system. The research presented here began before this consulting work and is not related to and was supported by this consulting work. Dr. Jacek K. Urbanek contributed to this article as an employee of Johns Hopkins University and the views expressed do not necessarily represent the views of Regeneron Pharmaceuticals Inc.- Published
- 2024
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