Sleep and circadian rhythm alterations in myalgic encephalomyelitis/chronic fatigue syndrome and post-COVID fatigue syndrome and its association with cardiovascular risk factors: A prospective cohort study

This study aimed to investigate circadian rhythm manifestations in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) patients (including a subpopulation of long-COVID patients) and matched healthy controls while also exploring their association with cardiovascular health variables. Thirty-one ME/CFS patients (75% females), 23 individuals diagnosed with post-COVID ME/CFS (56% females) and 31 matched healthy controls (68% females) were enrolled in this study. Demographic and clinical characteristics were assessed using validated self-reported outcome measures. Actigraphy data, collected over one week, were used to analyze the 24-h profiles of wrist temperature, motor activity, and sleep circadian variables in the study participants. Associations between lipid profile with endothelial dysfunction biomarkers (such as endothelin-1, ICAM-1 and VCAM-1) and with sleep and circadian variables were also studied. No differences were found in these variables between the two group of patients. Patients showed lower activity and worse sleep quality than matched healthy controls, together with a worse lipid profile than controls, that was associated with disturbances in the circadian temperature rhythm. ICAM-1 levels were associated with plasma lipids in healthy controls, but not in patients, who showed higher levels of endothelin-1 and VCAM-1. These findings suggest that lipid profiles in ME/CFS are linked to disrupted circadian rhythms and sleep patterns, likely due to endothelial dysfunction. Furthermore, they highlight the intricate relationship between sleep, circadian rhythms, and cardiovascular health in this condition.