A 2-day cardiopulmonary exercise test in chronic fatigue syndrome patients who were exposed to humidifier disinfectants.
Leem, Jong-Han, Jeon, Hyoung-Eun, Nam, Hun et al. · Environmental analysis, health and toxicology · 2022 · DOI
Quick Summary
This study tested whether a special two-day exercise test could detect post-exertional malaise (PEM)—the worsening of symptoms after physical activity—in people with ME/CFS who had been exposed to humidifier disinfectants. The researchers had 29 participants complete an exercise test, rest for 24 hours, then repeat it. They found that performance noticeably declined on the second day, showing that PEM is real and measurable.
Why It Matters
This research provides objective, measurable evidence that post-exertional malaise exists in ME/CFS patients—a finding that has sometimes been questioned by skeptics. The 2-day CPET protocol offers a standardized tool to document PEM and its physiological effects, potentially improving diagnosis, validating patient experiences, and enabling future treatment research.
Observed Findings
Peak oxygen consumption (VO2peak) significantly decreased between day 1 and day 2 exercise tests (p<0.001)
Oxygen consumption at ventilatory threshold (VO2@VT) significantly decreased on day 2 (p<0.001)
Time to reach peak oxygen consumption and ventilatory threshold were significantly reduced on day 2 (p<0.001)
Oxygen pulse at rest and at ventilatory threshold both decreased significantly on day 2 (p<0.001)
6-minute walk test distance was significantly reduced on day 2 (p<0.01)
Inferred Conclusions
Post-exertional malaise in CFS patients can be objectively measured and quantified using the 2-day CPET protocol
The 2-day CPET is a valid tool for differentiating between fatigue conditions in people with CFS symptoms
Physiological impairment following exercise exertion is reproducible and measurable in HD-exposed CFS patients
Abnormal PEM responses previously documented in general CFS populations also occur in HD-exposed individuals with CFS symptoms
Remaining Questions
How do these PEM responses compare quantitatively in HD-exposed versus non-exposed CFS patients, and in CFS patients versus healthy controls?
What This Study Does Not Prove
This study does not prove that humidifier disinfectant exposure causes ME/CFS, only that exposed individuals with CFS symptoms show PEM on testing. The lack of a control group (unexposed CFS patients, healthy controls, or unexposed people with fatigue) means we cannot determine if this PEM response is unique to HD-exposed populations or typical of CFS more broadly. The small sample size limits generalizability to the broader CFS population.