People with Long COVID and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Exhibit Similarly Impaired Vascular Function.
Mclaughlin, Marie, Sanal-Hayes, Nilihan E M, Hayes, Lawrence D et al. · The American journal of medicine · 2025 · DOI
Quick Summary
This study measured how well blood vessels work in people with long COVID and ME/CFS compared to healthy people. Researchers found that both long COVID and ME/CFS patients have similar problems with blood vessel function, even though ME/CFS patients have been sick much longer. These findings suggest that blood vessel problems may be an important part of how these illnesses develop.
Why It Matters
This research provides objective, measurable evidence of vascular dysfunction in ME/CFS, strengthening biological validity of the condition and supporting the hypothesis that blood vessel impairment may drive symptoms. The similarity between ME/CFS and long COVID patterns suggests common mechanisms and could guide development of targeted cardiovascular interventions for both populations.
Observed Findings
Long COVID patients showed mean FMD of 6.99 ± 4.33%, significantly lower than healthy controls at 11.30 ± 4.44%
ME/CFS patients showed mean FMD of 6.60 ± 3.48%, similarly impaired and not significantly different from long COVID patients
No statistically significant difference in FMD between long COVID and ME/CFS groups despite ME/CFS patients having 11.64 years longer mean illness duration
Both patient groups demonstrated impaired endothelial function indicative of increased cardiovascular risk
Study enrolled 51 total participants (17 per group) matched by age
Inferred Conclusions
Both long COVID and ME/CFS involve similarly impaired endothelial function, suggesting a shared vascular pathophysiological mechanism in post-viral illnesses
Vascular dysfunction may represent a core feature of these conditions rather than a consequence of prolonged illness duration
Improved cardiovascular monitoring and targeted interventions to restore endothelial function may be warranted in both populations to mitigate long-term health risks
Remaining Questions
Does vascular dysfunction develop early in post-viral illness or emerge progressively, and does it contribute causally to symptom severity?
What This Study Does Not Prove
This study does not prove that vascular dysfunction causes ME/CFS or long COVID symptoms—it only shows an association. The small sample size and one-time measurements cannot establish whether vascular impairment develops early in illness or emerges over time, nor can it explain the mechanisms underlying the dysfunction. The study also does not clarify whether treating vascular function would improve patient outcomes.
What specific mechanisms drive endothelial impairment in these post-viral conditions, and are they identical or distinct between long COVID and ME/CFS?
Could therapeutic interventions targeting vascular function (e.g., vasodilators, exercise, other treatments) improve clinical outcomes in these populations?
Does the degree of FMD impairment correlate with specific symptom patterns, disease severity, or functional limitations in ME/CFS and long COVID?