Ballouz, Tala, Menges, Dominik, Anagnostopoulos, Alexia et al. · BMJ (Clinical research ed.) · 2023 · DOI
This Swiss study followed over 1,100 people who had COVID-19 and compared them to people who never had the infection, tracking their recovery for two years. About 23% of infected people had not fully recovered by six months, and this number decreased only slightly to 17% by two years. Symptoms like loss of taste/smell, difficulty concentrating, fatigue, and post-exertional malaise (feeling worse after physical activity) were significantly more common in people who had COVID-19 compared to those who didn't.
This study provides crucial long-term evidence that post-COVID condition persists in a substantial proportion of patients beyond two years, with quantified symptom burden compared to controls—directly relevant to understanding the chronic disabling features shared with ME/CFS. The inclusion of post-exertional malaise and cognitive dysfunction as measurable outcomes aligns with ME/CFS core features, helping validate post-COVID as a condition with genuine physiological underpinnings. The heterogeneity in recovery trajectories highlighted here (some improving, some worsening, some fluctuating) reflects the complexity seen in ME/CFS and argues against one-size-fits-all interventions.
This study does not establish causation or mechanisms—it documents associations between prior COVID-19 infection and ongoing symptoms but does not explain why recovery is incomplete or variable. The reliance on self-reported recovery and symptoms, without objective biomarkers or standardized case definitions for post-COVID condition, limits the strength of inferences about true physiological recovery. The study does not evaluate treatment efficacy or identify which patients are at highest risk for persistent symptoms, nor does it directly compare post-COVID to ME/CFS or other post-viral conditions.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
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