Vercoulen, J H, Bazelmans, E, Swanink, C M et al. · Journal of psychiatric research · 1997 · DOI
This study looked at how active people with ME/CFS actually are compared to healthy people and patients with multiple sclerosis (MS). Researchers used three different methods to measure activity: questionnaires, daily logs, and a wearable device. They found that ME/CFS patients were less active than healthy people, similar to MS patients, but ME/CFS patients were more likely to avoid activities they feared would make their fatigue worse.
This study provides objective evidence that ME/CFS involves both reduced activity and distinct cognitive factors (fear of symptom exacerbation) that differentiate it from other conditions causing fatigue like MS. Understanding that activity avoidance in ME/CFS is partly driven by anticipatory cognitions is important for developing appropriate rehabilitation strategies that differ from those used for MS.
This cross-sectional design cannot establish causality—the study does not prove whether cognitive avoidance causes low activity, whether low activity causes fatigue, or whether fatigue causes avoidance. The study also does not assess post-exertional malaise (PEM) specifically or test whether activity interventions would improve outcomes. The finding that activity correlates with fatigue in ME/CFS but not MS does not explain the underlying biological mechanism.
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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