Assessment of overall essential tremor severity by monitoring with a wearable inertial sensor in real-life settings: an exploratory study

<h2>Abstract</h2><h3>Background</h3> Wearable digital technologies enable the objective monitoring and quantification of essential tremor (ET) in a real-world setting. <h3>Objective</h3> To quantify the overall severity of ET through continuous home monitoring using a wearable inertial sensor. <h3>Methods</h3> Twelve ET patients were monitored with an inertial sensor embedded in a smartwatch for an average of 11.61 ± 1.99 h per day over 6.67 ± 2.19 days. Overall tremor severity was defined based on the daily quantification of mild, moderate or severe tremor. Two scenarios were considered: 10 % (1) or 15 % (2) of the daily monitored time with higher tremor severity established the overall tremor severity, which was compared (Cohen's k) with that provided by the neurologists' assessment at the hospital and the patients' self-assessment at home using the Fahn Tolosa Marin Tremor Rating Scale. The effect of treatment on tremor severity was quantified using sensor data collected from eight patients. <h3>Results</h3> No or insignificant agreement was found between the overall tremor severity defined by continuous monitoring and that determined by the neurologist's assessment (Cohen's k = −0.113 and −0.277 for 10 % and 15 % scenarios, respectively) or patient self-assessment (Cohen's k = 0.133 and 0.168 for 10 % and 15 % scenarios, respectively). Neurologists underestimated the overall tremor severity with respect to continuous monitoring and patient self-assessment. Treatment was associated with a significant reduction in time with moderate (p = 0.034) and with moderate to severe (p = 0.027) tremor. <h3>Conclusions</h3> Continuous monitoring of ET with a wearable sensor provides more objective information about the overall tremor severity in a real-world setting and could more accurately quantify the response to treatment.