Clinical and Laboratory Characteristics of Fatigue-dominant Long-COVID subjects: A Cross-Sectional Study

Jin-Seok Lee; Yujin Choi; Jin-Yong Joung; Chang-Gue Son

doi:10.1016/j.amjmed.2024.01.025

Clinical and Laboratory Characteristics of Fatigue-dominant Long-COVID subjects: A Cross-Sectional Study

Am J Med. 2024 Feb 6:S0002-9343(24)00057-3. doi: 10.1016/j.amjmed.2024.01.025. Online ahead of print.

Authors

Jin-Seok Lee¹, Yujin Choi², Jin-Yong Joung³, Chang-Gue Son⁴

Affiliations

¹ Institute of Bioscience & Integrative Medicine, Daejeon University, Daehak-ro 75, Daejeon, 35235, Republic of Korea; Department of Korean Medicine, Korean Medical College of Daejeon University, Daehak-ro 62, Dong-gu, Daejeon, 34520, Republic of Korea.
² Department of Internal Medicine, College of Korean Medicine, Se-Myung University, Jecheon-si, 27136, Republic of Korea.
³ Department of Korean Medicine, Korean Medical College of Daejeon University, Daehak-ro 62, Dong-gu, Daejeon, 34520, Republic of Korea; Department of Internal Medicine, Daejeon Good-morning Oriental Hospital, 21, Dunsan-ro 123beon-gil, Seo-gu, Daejeon, 35240, Republic of Korea.
⁴ Department of Internal Medicine, College of Korean Medicine, Se-Myung University, Jecheon-si, 27136, Republic of Korea; Department of Korean Medicine, Korean Medical College of Daejeon University, Daehak-ro 62, Dong-gu, Daejeon, 34520, Republic of Korea. Electronic address: ckson@dju.ac.kr.

PMID: 38331137
DOI: 10.1016/j.amjmed.2024.01.025

Abstract

Background: Long-COVID is defined by persistent symptoms following COVID-19 infection. Approximately 71% of individuals with long-COVID experience ongoing fatigue, post-exertional malaise, and cognitive impairments, which share pathological similarities with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). This similarity has prompted studies to explore the characteristics of long-COVID to gain a better understanding of ME/CFS. To gain insights, we investigated the clinical and laboratory characteristics of individuals with fatigue-dominant long-COVID.

Methods: We enrolled 100 subjects (36 males, 64 females) with long-COVID who had a higher score than 60 in modified Korean version of the Chalder Fatigue Scale (mKCFQ11) and higher than 5 in fatigue-focused Visual Analogue Scale (VAS). To investigate fatigue symptoms, the mKCFQ11, the Multidimensional Fatigue Inventory (MFI-20), and VAS for fatigue and brain-fog, along with the Short Form Survey (SF-12) were employed. We also measured three cytokines and cortisol levels for immunological and endocrinological indicators. As a cross-sectional observational study, the data were collected at a single point in time.

Results: The mean scores on the measurements showed severe fatigue, and these scores were significantly correlated, with no differences based on sex, the post-COVID period, or age. Among the laboratory tests, plasma cortisol levels had a significant negative correlation with fatigue scores and a positive correlation with living quality. The negative correlation between cortisol levels and mKCFQ11 scores appeared to be more specific to mental fatigue than physical, which conflicted with other measurements.

Conclusion: Our findings provide the first insights into the characteristics of fatigue in individuals with long-COVID, particularly in terms of fatigue severity and cortisol levels. These results serve as valuable reference data for clinicians dealing with fatigue symptoms in long-COVID patients and for researchers exploring post-viral fatigue symptoms, including ME/CFS, in the future.

Keywords: Cortisol; Fatigue; HPA-axis; Long-COVID; ME/CFS.