E2 ModerateModerate confidencePEM not requiredCross-SectionalPeer-reviewedReviewed
Standard · 3 min
Descriptive epidemiology of chronic fatigue syndrome based on a nationwide survey in Japan.
Minowa, M, Jiamo, M · Journal of epidemiology · 1996 · DOI
Quick Summary
Researchers surveyed hospitals across Japan in 1992 to understand how many people have ME/CFS and how it spreads. They found that about 0.85 cases per 100,000 people were diagnosed that year, with slightly more women affected than men. The number of cases appeared to be growing from 1992 to 1993, and a small percentage of cases started after an infection.
Why It Matters
This is one of the few nationwide epidemiological surveys of ME/CFS using standardized diagnostic criteria, providing important international prevalence data beyond Western populations. The identification of an increasing trend and post-infectious cases offers insights into disease burden and potential etiopathogenic factors in a large developed economy.
Observed Findings
Period prevalence adjusted for response rate was 0.85 per 100,000 population in 1992 (0.63 males, 1.02 females)
Point prevalence increased from 0.40 per 100,000 on January 1, 1992 to 0.60 per 100,000 on January 1, 1993
Incidence of new cases in 1992 was 0.46 per 100,000 person-years
Post-infectious CFS accounted for 14.8% of cases, with slightly higher proportion in females
Three clusters of two cases each were reported
Inferred Conclusions
ME/CFS affects approximately 0.85 per 100,000 Japanese residents annually, with female predominance
ME/CFS showed an increasing prevalence trend during the early 1990s in Japan
A subset of ME/CFS cases follow infectious illness, though post-infectious etiology is not universal
Geographic clustering of cases may suggest possible environmental or transmissible factors in some instances
Remaining Questions
What is the true population prevalence when including non-hospitalized and primary care patients?
What infectious agents, if any, trigger post-infectious ME/CFS, and why do some but not all infections lead to the condition?
What This Study Does Not Prove
This hospital-based survey cannot establish true population prevalence because many ME/CFS patients do not seek care or are seen in outpatient settings not captured by the study. The finding that 14.8% of cases were post-infectious does not prove infection causes ME/CFS, nor does it establish that the remaining 85% have different etiologies. Case clusters are reported descriptively without epidemiological analysis to determine if they represent true clustering.
Tags
Symptom:Fatigue
Phenotype:Infection-Triggered
Method Flag:No ControlsSex-StratifiedWeak Case Definition
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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