Sunada, Naruhiko, Nakano, Yasuhiro, Otsuka, Yuki et al. · Journal of clinical medicine · 2022 · DOI
This study looked at sleep problems in 363 long COVID patients in Japan and found that about 16.5% had significant sleep disturbance. People infected during the Omicron wave were twice as likely to have sleep problems compared to those infected during the Delta wave. Patients with sleep disturbance also reported more fatigue, brain fog, headaches, and anxiety, and had abnormal stress hormone levels suggesting their bodies were under persistent stress.
Sleep disturbance is a significant symptom in long COVID and shares overlapping pathophysiology with ME/CFS, including immune and endocrine dysfunction. Understanding that sleep problems correlate with neuroendocrine stress markers and variant-specific prevalence may help researchers identify underlying mechanisms and develop targeted treatments for post-viral fatigue disorders.
This study does not establish causality—it cannot prove that the Omicron variant directly causes sleep disturbance or that hormonal changes cause (rather than result from) sleep problems. The cross-sectional design captures only a single time point and cannot determine whether sleep disturbance precedes or follows other long COVID symptoms, nor can it account for recall bias in symptom reporting.
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
Sunada, Naruhiko, Nakano, Yasuhiro, Otsuka, Yuki, Tokumasu, Kazuki, Honda, Hiroyuki, Sakurada, Yasue, et al. (2022). Characteristics of Sleep Disturbance in Patients with Long COVID: A Retrospective Observational Study in Japan.. Journal of clinical medicine. https://doi.org/10.3390/jcm11247332
BibTeX
@article{mecfsatlas-sunada-2022-characteristics-sleep,
author = {Sunada, Naruhiko and Nakano, Yasuhiro and Otsuka, Yuki and Tokumasu, Kazuki and Honda, Hiroyuki and Sakurada, Yasue and Matsuda, Yui and Hasegawa, Toru and Omura, Daisuke and Ochi, Kanako and Hagiya, Hideharu and Ueda, Keigo and Kataoka, Hitomi and Otsuka, Fumio},
title = {Characteristics of Sleep Disturbance in Patients with Long COVID: A Retrospective Observational Study in Japan.},
journal = {Journal of clinical medicine},
year = {2022},
doi = {10.3390/jcm11247332},
note = {PubMed: 36555948},
url = {https://www.mecfsatlas.com/evidence/sunada-2022-characteristics-sleep},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-30. https://www.mecfsatlas.com/evidence/sunada-2022-characteristics-sleep
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