E0 ConsensusModerate confidencePEM not requiredMeta-AnalysisPeer-reviewedReviewed
Prevalence of Chronic Fatigue Syndrome (CFS) in Korea and Japan: A Meta-Analysis.
Lim, Eun-Jin, Son, Chang-Gue · Journal of clinical medicine · 2021 · DOI
Quick Summary
This study looked at how common ME/CFS is in Korea and Japan by reviewing eight existing studies. Researchers found that about 0.76-0.77% of people in these countries have ME/CFS—meaning roughly 1 in 130 people. Women were affected about twice as often as men in Korea, though this difference was smaller in Japan.
Why It Matters
This is one of the first systematic reviews of ME/CFS prevalence in Asian populations, filling an important gap in our understanding of how common this disease is globally. The variation in gender differences between countries raises questions about whether cultural, genetic, or diagnostic factors influence who develops and is diagnosed with ME/CFS.
Observed Findings
- ME/CFS prevalence in Korea was 0.77% (95% CI 0.34-1.76) and in Japan was 0.76% (95% CI 0.46-1.25).
- Female prevalence in Korean studies was approximately 1.31%, compared to 0.60% in males.
- Female prevalence in Japanese studies was 0.76%, compared to 0.65% in males.
- Only eight population-based prevalence studies were identified across both countries.
Inferred Conclusions
- ME/CFS prevalence appears similar in Korea and Japan, suggesting relatively consistent disease burden across these Asian nations.
- Gender differences in ME/CFS prevalence vary by country, with Korea showing a stronger female predominance than Japan.
- More rigorous epidemiological research is needed to clarify gender-specific prevalence patterns and underlying mechanisms.
Remaining Questions
- Why does the female-to-male prevalence ratio differ significantly between Korea and Japan?
- How do diagnostic practices, healthcare-seeking behavior, and cultural factors contribute to reported prevalence differences across countries?
- What is the true prevalence of ME/CFS in other Asian countries beyond Korea and Japan?
What This Study Does Not Prove
This study does not explain why ME/CFS occurs or identify causes of the disease. It also cannot determine whether the gender differences reflect true biological differences in disease susceptibility or differences in how men and women are diagnosed and reported across countries. The prevalence estimates have wide confidence intervals, indicating substantial uncertainty.
Tags
Symptom:Unrefreshing SleepFatigue
Method Flag:PEM Not DefinedWeak Case DefinitionSex-Stratified
Metadata
- DOI
- 10.3390/jcm10153204
- PMID
- 34361987
- Review status
- Editor reviewed
- Evidence level
- Higher-level evidence type — systematic reviews, meta-analyses, guidelines, or major syntheses (study type, not a quality guarantee)
- Last updated
- 12 April 2026
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 →
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