Novel Wasserstein distance-based sleep-activity regularity metrics from wearable data for healthy aging: J-HAS

As the global population ages, understanding determinants of healthy aging requires evidence on whether the regularity of sleep and physical activity, beyond total duration or volume, is associated with health outcomes. In J-HAS, a prospective observational cohort study, we developed novel Wasserstein distance-based regularity metrics using wearable data and examined associations with cognitive and physical function among Japanese adults aged 80–96 years. Among 150 enrolled participants, 120 had complete follow-up data, contributing 46,720 person-days of sleep recordings and 28,180 person-days of physical activity recordings. Higher sleep Wasserstein regularity (SWR) and activity Wasserstein regularity (AWR) scores indicate greater temporal regularity. Higher all-day SWR was associated with better cognitive performance; each 1-unit increase in rescaled SWR corresponded to approximately 1.6- to 1.7-fold higher odds of being in the second and third MoCA-J tertiles than in the lowest tertile. All-day SWR was not associated with 5-times-sit-to-stand performance or grip strength. Higher midday and evening SWR were associated with faster sit-to-stand performance. All-day AWR showed no significant associations. Midday AWR was inversely associated with grip strength in secondary analyses. The SWR-cognition association remained robust after FDR correction in continuous outcome ( q = 0.003) and absolute-scaling analyses ( q = 0.045). Wasserstein-based wearable metrics may inform personalized healthy-aging strategies.