Continuous Monitoring of Essential Tremor Using a Portable System Based on Smartwatch

Essential tremor (ET) shows amplitude fluctuations throughout the day, presenting challenges in both clinical and treatment monitoring. Tremor severity is currently evaluated by validated rating scales, which only provide a timely and subjective assessment during a clinical visit. Motor sensors have shown favorable performances in quantifying tremor objectively. A new highly portable system was used to monitor tremor continuously during daily lives. It consists of a smartwatch with a triaxial accelerometer, a smartphone, and a remote server. An experiment was conducted involving eight ET patients. The average effective data collection time per patient was 26 (±6.05) hours. Fahn-Tolosa-Marin Tremor Rating Scale (FTMTRS) was adopted as the gold standard to classify tremor and to validate the performance of the system. Quantitative analysis of tremor severity on different time scales is validated. Significant correlations were observed between neurologist's FTMTRS and patient's FTMTRS auto-assessment scores ( = 0.84; = 0.009), between the device quantitative measures and the scores from the standardized assessments of neurologists ( = 0.80; = 0.005) and patient's auto-evaluation ( = 0.97; = 0.032), and between patient's FTMTRS auto-assessment scores day-to-day ( = 0.87;