Cytokine responses to exercise and activity in patients with chronic fatigue syndrome: case-control study.
Level 4 - case-series / case-control
Case-control study comparing chronic fatigue syndrome patients with matched healthy controls.
PubMed 28779554 · doi:10.1111/cei.13023
What was done
Twenty-four patients meeting CDC criteria for chronic fatigue syndrome (CFS) without comorbid psychiatric disorders were recruited from two UK clinics along with 21 age- and sex-matched sedentary healthy controls. Circulating protein and RNA levels were measured for TGF-β, TNF, IL-8, IL-6, and IL-1β, alongside protein levels of IL-2, IL-4, IL-5, IL-10, IL-12p70, and IFN-γ. Blood samples were collected at rest and before and after both commuting and standardized aerobic exercise over a 9-day observation period.
What was found
Resting TGF-β protein concentrations initially appeared elevated in CFS patients compared to controls (median [quartiles]: 43.9 [19.2, 61.8] vs 18.9 [16.1, 30.0] ng/ml; P = 0.003), but this was identified as a spurious finding caused by assay batch variation. There were no differences between groups in TGF-β changes after commuting or exercise. All other cytokine protein and RNA levels were similar between cases and controls, and post-exertional symptoms and perceived effort were not associated with cytokine increases.
Why it matters
This study fails to replicate earlier findings of elevated TGF-β in CFS, suggesting circulating cytokines do not play a central role in post-exertional symptom exacerbation in these patients.
Limits
The sample size was small (24 cases, 21 controls), limiting statistical power. The study excluded patients with psychiatric comorbidities, which may limit generalizability. Circulating cytokine concentrations may not reflect localized tissue or neuroimmune alterations.
Cited by
- contradicts Studies show that in individuals with chronic fatigue syndrome, inflammatory markers and energetic stress signals skyrocket after exercise, leading to post-exertional malaise.