Prevalence, trajectory over time, and risk factor of post-COVID-19 fatigue.

Fatigue is one of the most commonly reported symptoms in the context of the post-COVID-19 syndrome. Notably, fatigue is characterised by overlapping physical and psychopathological symptoms, and questions about its trajectory over time and possible predictors remained unanswered. Thus, in the present study we aim to investigate the prevalence, the course over time, and the risk factors of post-COVID fatigue. We included 495 patients recovered from COVID-19. For all of them we collected one month demographic, clinical and psychopathological characteristics. We evaluated fatigue severity at one, three, six, and twelve-months according to Fatigue Severity Scale (FSS). We explored the potential predictor of long-term post-COVID fatigue (six or twelve months FSS) by implementing 5000 non-parametric bootstraps enhanced elastic net penalised regression. We found that 22%, 27%, 30%, and 34% of patients self-rated fatigue symptoms in the pathological range at one, three, six, and twelve months respectively. We detected a worsening of fatigue symptomatology over time. From the elastic net regression results, only depressive symptomatology at one month (ZSDS and BDI-13) predicted the presence of post-COVID-19 long-term fatigue. No other clinical or demographic variable was found to predict post-COVID fatigue. We suggest that, rather independent of COVID-19 severity, depression after COVID-19 is associated with persistent fatigue. Clarifying mechanisms and risk factors of post-COVID fatigue will allow to identify the target population and to tailor specific treatment and rehabilitation interventions to foster recovery.