Peak 30-minute cadence as a digital biomarker of real-world mobility in people with multiple sclerosis

Purpose: This study examined whether accelerometer-derived Peak 30-Minute Cadence (Peak-30_CAD) could serve as a digital biomarker of real-life mobility in people with multiple sclerosis (MS). Methods: Fifty-four participants (37.96±10.25 years; BMI = 26.54 ± 5.18 kg/m²) with relapsing-remitting MS participated in the study. Participants underwent clinical and functional assessments, including the Expanded Disability Status Scale, Patient-Determined Disease Steps (PDDS), Timed Up and Go (TUG), and the 6-Minute Walk Test (6MWT). Free-living physical activity data were collected using a hip-worn accelerometer for seven consecutive days and used to derive common physical activity metrics, including moderate to vigorous physical activity, steps per day, and peak one-minute cadence (Peak-1_CAD). Peak-30_CAD metric was calculated as the mean of the highest 30 non-consecutive minutes of step cadence per day and averaged across valid days of wear time. Results: Peak-30_CAD was the only free-living metric significantly correlated with all clinical mobility measures (PDDS, r = -0.525; TUG, r = -0.293; and 6MWT, r = 0.495), such that lower Peak-30_CAD values were associated with higher disability levels and reduced walking capacity. Of note, participants with disability (PDDS 1–4) had significantly lower 6MWT distances (-99.9 m, P = 0.001) and Peak-30_CAD values (-23.8 steps/min, P < 0.001) than those without disability (PDDS = 0). The effect size for Peak-30_CAD was larger than for 6MWT, suggesting higher potential for Peak-30_CAD in differentiating disease status than the 6MWT. Conclusion: These findings support Peak-30_CAD as a valid digital biomarker for assessing mobility in people with MS under real-world conditions.