The importance of physiological data variability in wearable devices for digital health applications

Abstract

<p>This paper aims at characterizing the variability of physiological data collected through a wearable device (Empatica E4), given that both intra- and inter-subject variability play a pivotal role in digital health applications, where Artificial Intelligence (AI) techniques have become popular. Inter-beat intervals (IBIs), ElectroDermal Activity (EDA) and Skin Temperature (SKT) signals have been considered and variability has been evaluated in terms of general statistics (mean and standard deviation) and coefficient of variation. Results show that both intra- and inter-subject variability values are significant, especially when considering those parameters describing how the signals vary over time. Moreover, EDA seems to be the signal characterized by the highest variability, followed by IBIs, contrary to SKT that results more stable.<br />This variability could affect AI algorithms in classifying signals according to particular discriminants (e.g. emotions, daily activities, etc.), taking into account the dual role of variability: hindering a net distinction between classes, but also making algorithms more robust for deep learning purposes thanks to the consideration of a wide test population. Indeed, it is worthy to note that variability plays a fundamental role in the whole measurement chain, characterizing data reliability and impacting on the final results accuracy and consequently on decision-making processes.</p>

Methods for the metrological characterization of wearable devices for the measurement of physiological signals: state of the art and future challenges

“…Particular attention should be paid to physiological variability, which cannot be avoided and undoubtedly impacts on both measurement results and evaluation procedures; indeed, whereas in mechanical or electrical measurements repeated measures can be performed on the same measurand in the same conditions, when evaluations are carried out on a human being the subjectivity plays a pivotal role that cannot be ignored [41] . Hence, given the physiological variability intrinsic of human measurands, it would be important to change the point of view: again, we are not in front of mechanical, electrical, or thermal quantities, whose measurement can be repeated.…”