Because there are so many case definitions, it is difficult to estimate how many people suffer from ME/CFS. Using a very broad case definition, such as the Oxford Case Definition (which only requires six months of fatigue) would result in enormously inflated numbers, as it could capture people with depression, deconditioning, and rare diseases, such as Behçet’s, Ehlers-Danlos, Primary Immune Deficiency, early MS, rare forms of leukemia, and many others.
A narrow case definition, such as the Canadian Consensus Criteria or International Consensus Criteria, would produce more accurate statistics, but these definitions are used almost exclusively by ME/CFS experts, not by government agencies charged with establishing prevalence and incidence. The fact that so few doctors have the expertise to diagnose ME/CFS confounds the problem.
In 2003, Reyes et al. published a 4-year study conducted in Wichita, Kansas. The overall prevalence of CFS was 235 per 100,000 persons, which meant 800,000 people in the U.S. would have the disease. CFS was more than four times more common among women (373 per 100,000) than among men (83 per 100,000). Only 16 percent had received a diagnosis and medical treatment for their illness. Although the Wichita study was published more than 10 years ago, statistics for the US have not significantly changed. According to the CDC, there are currently more than one million people in the U.S. with ME/CFS.
Worldwide, there may be as many as 17 – 24 million people with ME/CFS.
In Great Britain, there are roughly 250,000 people with ME/CFS. One study estimated the minimum prevalence rate of ME/CFS at 0.2%. (Nacul et al.) ME/CFS Australia estimated that there were 180,000 Australians with ME in 2002. That number has since grown.
The 2005 Community Health Survey conducted by Statistics Canada indicated that there were 333,816 Canadians diagnosed with ME/CFS.
In the Netherlands, prevalence may be as high as 3.6% in the working population, which is considerably higher than the US rate. (Huibers et al.) Sweden has also reported a high prevalence rate of 2.6%. (Evengård et al.) There have been very few systematic epidemiological studies conducted in Africa, but one study suggested that the rates might be higher in Nigeria than in the US. (Njoku et al.) The prevalence of CFS in a community population in Japan was 1.0% in 2011, which is roughly equivalent to the US prevalence rate.
Leonard A. Jason, Nicole Porter, Molly Brown, Valerie Anderson, Abigail Brown, Jessica Hunnell, and Athena Lerch. Jason LA, Porter N, Brown M, et al. CFS: A Review of Epidemiology and Natural History Studies. Bulletin of the IACFS/ME. 2009;17(3):88-106.
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Hamaguchi M1, Kawahito Y, Takeda N, Kato T, Kojima T. “Characteristics of chronic fatigue syndrome in a Japanese community population : chronic fatigue syndrome in Japan.” Clin Rheumatol. 2011 Jul;30(7):895-906. doi: 10.1007/s10067-011-1702-9. Epub 2011 Feb 8.
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Nacul Luis C; Eliana M Lacerda, Derek Pheby, Peter Campion, Mariam Molokhia, Shagufta Fayyaz, Jose CDC Leite, Fiona Poland, Amanda Howe, and Maria L Drachler.“Prevalence of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) in three regions of England: a repeated cross-sectional study in primary care.” BMC Medicine 2011, 9:91 doi:10.1186/1741-7015-9-91.
Njoku MG1, Jason LA, Torres-Harding SR. “The prevalence of chronic fatigue syndrome in Nigeria. J Health Psychol.” 2007 May;12(3):461-74
Reyes M, Nisenbaum R, Hoaglin DC, Unger ER, Emmons C, Randall B, Stewart JA, Abbey S, Jones JF, Gantz N, Minden S, Reeves WC. Arch Intern Med. “Prevalence and incidence of chronic fatigue syndrome in Wichita, Kansas.” Arch Intern Med. 2003 Jul 14;163(13):1530-6. 2003 Jul 14;163(13):1530-6.
Son, Chang-Gue. Review of the Prevalence of Chronic Fatigue Worldwide. The Journal of Korean Oriental Medicine, 2012. Vol.33. No.2. 25-33.