Long-Term Physical Activity Patterns and Incident Kidney Stone Risk: A Wearable-Based Survival Analysis in U.S. Cohort

PURPOSE: Physical activity has been associated with reduced kidney stone risk, yet objective, long-term activity patterns captured by wearable devices remain understudied. We evaluated the association between longitudinal physical activity metrics and incident kidney stone events using continuous Fitbit-derived data. METHODS: research program. Participants included Fitbit users without prior kidney stone disease who had valid step and heart rate (HR) data during a 180-day baseline window. We defined an HR valid day as ≥600 minutes of wear time, consistent with established wearable validity standards. We fit Cox proportional hazards models to evaluate associations between daily steps, active minutes, and sedentary time with incident stone events, adjusting for demographic and clinical covariates. RESULTS: Among 9376 participants in the final analytic cohort, 1% (103 participants) developed an incident stone event during follow-up. Higher daily step counts were independently associated with a lower hazard of developing a stone event (adjusted HR per 1000 steps/day 0.92, 95% confidence interval 0.86-0.99). Moderate-to-vigorous physical activity minutes showed a protective trend, while sedentary time was not associated with stone incidence. CONCLUSIONS: Long-term physical activity, particularly step volume, is inversely associated with incident kidney stone events. These findings support the potential of physical activity as a modifiable behavioral target for stone prevention and demonstrate the feasibility of risk stratification using wearable devices.