Persistent Multi-System Impairments Detected by Wearable Monitoring in Long COVID Cases reporting Fatigue up to Three Years Post-Infection

Long COVID remains poorly understood and previous studies have mainly focused on describing symptoms or single-system health deficits in severe cases. In the CONVALESCENCE case-control study, 306 community-based participants (aged 57[IQR 41-63], 80% female) were enrolled 2.0 [1.7, 2.5] years post-infection and were monitored for 12 months using a smartwatch and apps to assess mental health, cognitive function, physical activity, exercise capacity, cardiorespiratory function, autonomic function and sleep. Compared to controls (N=152), long COVID cases with fatigue-cluster symptoms (N=50) presented small persistent deficits across all systems with no evidence of recovery over 12 months. Participants with fatigue-cluster symptoms not attributable to long COVID (N=28) showed a similar trend, while participants with prior long COVID but no fatigue-cluster symptoms (N=76) were not different from controls. The lack of significant recovery between years two and three post-infection demonstrates protracted multi-system deficits for fatigue-cluster cases and highlights ongoing needs to better understand and manage long COVID.