Nakano, Yasuhiro, Otsuka, Yuki, Honda, Hiroyuki et al. · Medicina (Kaunas, Lithuania) · 2022 · DOI
This study compared long COVID symptoms in patients infected with different COVID-19 variants (Delta vs. Omicron) in Japan. Patients infected with Omicron had milder initial illness but were more likely to experience fatigue, sleep problems, and ongoing cough. Those infected with Delta were more likely to lose their sense of taste or smell and experience hair loss.
Understanding how different COVID-19 variants produce distinct long-term symptom patterns helps clinicians recognize and manage post-COVID conditions more effectively. For ME/CFS researchers, this study provides evidence that fatigue-predominant presentations may be variant-dependent, which could inform investigation of biological mechanisms driving persistent fatigue and post-exertional malaise in long COVID.
This study does not prove that viral variants directly cause specific symptom patterns—hospitalization rates and vaccination status also differed between groups and could contribute to symptom differences. Correlation between variant type and symptom presentation does not establish the biological mechanisms responsible. The retrospective design and single Japanese center limit generalizability to other populations.
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 →
The first block is for the primary paper and is the citation you should use in research work. The atlas-snapshot line only applies if you are specifically referring to this atlas’s reading of the paper on the date shown.
Primary citation
Nakano, Yasuhiro, Otsuka, Yuki, Honda, Hiroyuki, Sunada, Naruhiko, Tokumasu, Kazuki, Sakurada, Yasue, et al. (2022). Transitional Changes in Fatigue-Related Symptoms Due to Long COVID: A Single-Center Retrospective Observational Study in Japan.. Medicina (Kaunas, Lithuania). https://doi.org/10.3390/medicina58101393
BibTeX
@article{mecfsatlas-nakano-2022-transitional-changes,
author = {Nakano, Yasuhiro and Otsuka, Yuki and Honda, Hiroyuki and Sunada, Naruhiko and Tokumasu, Kazuki and Sakurada, Yasue and Matsuda, Yui and Hasegawa, Toru and Ochi, Kanako and Hagiya, Hideharu and Kataoka, Hitomi and Ueda, Keigo and Otsuka, Fumio},
title = {Transitional Changes in Fatigue-Related Symptoms Due to Long COVID: A Single-Center Retrospective Observational Study in Japan.},
journal = {Medicina (Kaunas, Lithuania)},
year = {2022},
doi = {10.3390/medicina58101393},
note = {PubMed: 36295554},
url = {https://www.mecfsatlas.com/evidence/nakano-2022-transitional-changes},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-28. https://www.mecfsatlas.com/evidence/nakano-2022-transitional-changes
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