SARS-CoV-2 infection is associated with physical but not mental fatigue - Findings from a longitudinal controlled population-based study

Objective: Fatigue has been identified as the core symptom of long-Covid, however, putative pandemic -related influences remain largely unclear. We investigated trajectories of total, physical and mental fatigue and the factors associated with it in previously infected and non -infected individuals up to one year post- infection. Methods: We used data from a longitudinal cohort study of German adults with two samples: A representative probability sample and a sample of individuals with proven SARS-CoV-2 infection. Surveys were conducted in spring 2020(T1), autumn 2020(T2) and summer 2021(T3). Fatigue was assessed using the FAS, distinguishes between physical and mental fatigue. Depression, anxiety and stress were assessed using PHQ-4 and PSQ. Results: 1990 participants [mean age 47.2 (SD =17.0), 30.5% previously infected] were included in the survey at T1 (n = 1118 at T2, n = 692 at T3). Total and physical fatigue, but not mental fatigue were significantly higher in the previously infected compared to the non -infected sample at T2, but this group difference disappeared at T3. We identified Covid-infection as a factor associated with transient total and physical fatigue at T2. Depression, anxiety and stress at T1 were associated with total, physical and mental fatigue at both follow-ups. Conclusions: Our results highlight the importance of considering physical and mental fatigue as separate entities, while suggesting a greater relevance of the physical signs of fatigue in understanding long-Covid. The results further showed that baseline mental health symptoms were the most strongly associated with fatigue trajectories.