Digital Activity Markers in Chronic Inflammatory Demyelinating Polyneuropathy.

Objective: To evaluate the utility of smartwatch and smartphone-based activity metrics for assessing disease severity and quality of life in patients with chronic inflammatory demyelinating polyneuropathy (CIDP).

Methods: In the electronic monitoring of disease activity in patients with CIDP (EMDA-CIDP) trial, we performed a prospective observational study from January 2023 to July 2024 at university hospitals in Düsseldorf and Münster, with an independent validation cohort in Hannover. Eligible participants were adults with CIDP on stable intravenous immunoglobulin (IVIG) therapy. Clinical evaluations included established disability scales (I-RODS and INCAT) and quality of life assessments. Activity metrics were captured via consumer-grade smartwatches, with adherence criteria applied to ensure data quality. A real-world smartphone-based cohort of 20 patients was used as a comparator.

Results: Among 46 participants (median age 64 Years [IQR 57-69]; 24% female), smartwatch-derived maximum daily-step count emerged as a robust indicator of disease severity. In 43 patients meeting wearable adherence criteria, maximum daily steps showed strong correlations with clinical scores, positively with I-RODS (Spearman's ρ = 0.74) and inversely with INCAT (Spearman's ρ = -0.54). Additional smartwatch metrics correlated with quality of life domains, whereas smartphone-derived metrics of a validation cohort exhibited weaker correlations.

Interpretation: These results indicate that smartwatches many patients already use can yield valuable, objective data for assessing disease status in CIDP. Integrating smartwatch-derived metrics into clinical assessments may enhance traditional evaluations and deepen understanding of disease progression and patient quality of life. These promising results warrant additional, larger-scale studies in the future.