Exploring digital biomarkers using smartphones for fatigue assessment in patients with multiple sclerosis

The treatment goals for multiple sclerosis (MS) are shifting from relapse inhibition to the improvement of long‐term prognosis and quality of life (QoL). Fatigue reduces QoL in patients with MS. The methods for assessing and treating fatigue, particularly those that are easily applicable in clinical settings remain unestablished. This study aimed to explore and identify digital biomarkers related to fatigue using smartphones.The patients with MS attending the Department of Neurology at St. Marianna University School of Medicine (Kanagawa, Japan) were surveyed via mail and responses were obtained online. The survey items included patient background such as age and sex, Fatigue Assessment Scale (FAS), which is one of the patient‐reported outcomes (PROs) and serves as a questionnaire method for assessing fatigue, as well as self‐assessments of depression, sleep, and pain. Additionally, the number of steps recorded on smartphones was collected as personal health records (PHRs) along with the time spent using smartphones.Overall, 27 (18 female) participants responded (response rate: 46.6%). The mean age was 41.0 ± 14.6 y and the majority (12 participants) had a disease duration of <5 y. According to self‐assessments, moderate or higher symptoms of depression, sleep disturbances, and pain were observed in 13 participants, 10 participants, and 6 participants, respectively. The daily number of steps ranged from 805 to 15 263 (median of 4514 steps). The number of steps was negatively correlated with FAS (r = −0.47, P = .02), and in cases with any physical disability, the number of steps was negatively correlated with FAS (r = −0.69, n = 0.01).The number of steps automatically measured by smartphones could be a digital biomarker reflecting fatigue in MS patients.