How Hormones and Daily Rhythms could Affect ME/CFS and Long COVID in a new Protocol
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A recent study protocol published in npj Women’s Health explored how hormonal fluctuations, daily rhythms, and molecular changes influence symptoms in women with ME/CFS and long COVID. The MELLOW study (ME/CFS + Long COVID Longitudinal Omics and Women’s Health) focused on reproductive-aged women, who are disproportionately affected by these conditions, to understand how sex and stress hormones might contribute to fatigue, cognitive difficulties, sleep disturbances, and post-exertional malaise (PEM).
Researchers used a chronobiology-based approach, tracking participants across their menstrual cycles and daily rhythms. Participants wore devices to monitor heart rate, sleep, and activity, collected urine and small blood samples to measure hormones and molecular markers, and completed daily symptom surveys. By capturing repeated measurements over time, the study could map how biological changes corresponded with symptom fluctuations.
The MELLOW study integrated multi-omics data—including genomics, proteomics, metabolomics, and steroid hormone profiling—with physiological monitoring. This approach allowed the researchers to identify patterns that could explain why symptoms vary across the day and menstrual cycle. The findings provide new insights into the underlying biology of ME/CFS and long COVID in women and highlight the importance of considering hormonal and circadian rhythms in research and treatment development.
It’s important to note that this publication describes a new study protocol rather than presenting new clinical data. While results are not yet available, the significance lies in the design itself: it establishes a rigorous framework for integrating hormonal, molecular, and symptom tracking in a way that could finally clarify the complex biology behind ME/CFS and long COVID. The fact that such a comprehensive, chronobiology-informed study is being launched is an important step forward for research in these conditions.