Association of acute COVID-19 severity and long COVID fatigue and quality of life: Prospective cohort multicenter observational study.

Long COVID, or post-COVID-19 condition, is characterized by symptoms persisting beyond 12 weeks after severe acute respiratory syndrome coronavirus 2 infection, affecting individuals regardless of acute disease severity. Fatigue - often linked with depression and anxiety - is among its most debilitating manifestations. However, the associations between fatigue subtypes (physical vs mental), mental health symptoms, and acute disease severity on long-term health-related quality of life (HRQoL) remain unclear. This study examines the relationships between long COVID fatigue, depression, anxiety, acute disease severity, and HRQoL in a post-COVID-19 cohort. This prospective observational cohort study was conducted across 5 Portuguese hospitals between November 2020 and June 2022. Adults (≥18 years) with confirmed severe acute respiratory syndrome coronavirus 2 infection ≥6 months prior and fulfilling World Health Organization criteria for long COVID were included. Acute Coronavirus disease 2019 (COVID-19) severity was classified per World Health Organization definitions. The sampling strategy included patients across the severity spectrum. At 3 months postinfection (T1), patients received physician-led clinical assessments. At 6 months (T2), they attended in-person follow-up visits, completing standardized forms and validated questionnaires assessing post-acute sequelae. Fatigue was reported both binarily (yes/no) and via the chalder fatigue scale (11-item version). Anxiety and depression were assessed using the hospital anxiety and depression scale; post-traumatic stress disorder symptoms with the 14-item post-traumatic stress scale; and HRQoL with the EuroQol-5 dimensions. Descriptive statistics, analysis of variance, chi-square, and correlation analyses (Pearson's or Spearman's) were used to evaluate associations. Analyses were performed using SPSS (v27; IBM Corp., Amonk). Among 208 patients, fatigue was significantly associated with anxiety and depression (P < .001). Physical fatigue correlated more strongly with depression (r = 0.65, P < .001) and anxiety (r = 0.58, P < .001) than mental fatigue (r = 0.50 and R = 0.48, respectively; P < .001). Surprisingly, severe acute COVID-19 cases reported lower fatigue (CFQ: 13.3 ± 8.4) than mild (17.7 ± 7.2) or moderate (17.4 ± 8.0) cases (P < .005), and higher HRQoL (EuroQol visual analog scale: 74.3 ± 20.3, P = .002). Anxiety symptoms were more common in mild cases (P < .001); post-traumatic stress disorder symptoms did not differ by severity. Long COVID fatigue - especially physical - is strongly linked to depression and anxiety. Mild/moderate acute COVID-19 cases show greater fatigue and lower HRQoL than severe cases, highlighting the need for tailored long-term care regardless of initial severity.