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Background Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a chronic disabling illness characterized by activity limitations associated with fatigue, post-exertional malaise (PEM), unrefreshing sleep, memory and concentration problems, orthostatic intolerance and painful discomfort. While typically considered to be a chronic condition, some persons who have had ME/CFS report no longer having the disorder. Here, the prevalence and characteristics of adults in the United States who self-report having an ME/CFS diagnosis and those who self-report no longer having ME/CFS are presented. Methods The current study utilized publicly available data from the 2021–2023 National Health Interview Survey, which interviewed 86,655 United States civilian non-institutionalized adults about their health. For this study, participants were categorized into three groups: Current ME/CFS (individuals currently diagnosed with ME/CFS), Past ME/CFS (individuals who were previously diagnosed but no longer report having the condition), and Never ME/CFS (individuals who have never been diagnosed with ME/CFS). These groups were characterized using descriptive statistics. Results In the United States adult population, 20.7% of the estimated 1.5% adults who ever received an ME/CFS diagnosis report they no longer have the condition (Past ME/CFS). Overall the Past ME/CFS group reported experiencing symptoms less frequently, less difficulty with daily living, approximately equal prevalence of comorbidities, and better general health status than the Current ME/CFS group but remained significantly impaired compared to the Never ME/CFS group. However, 40–50% of adults with Past ME/CFS report symptoms and function similar to adults with Current ME/CFS and only approximately 25% had substantially less symptoms and better function compared to those with Current ME/CFS. Comorbidities did not differ significantly between the Current and Past ME/CFS groups. Conclusion Further study to better understand the reasons why those in the Past ME/CFS group report no longer having the disorder is important for understanding the natural history and disease burden of ME/CFS. Studying symptomatic remissions, and the underlying physiology of improvement, could lead to identification of new disease modifying therapeutic approaches.