The lack of a standardized definition for Chronic Fatigue Syndrome (CFS) means its prevalence is difficult to estimate.
Overall, evidence suggests a prevalence of about 0.25% to 0.40% which represents about 40 people in every 10,000 visiting a general practice. Epidemiological data for the UK is lacking but estimates based on data from other countries suggest there may be around 4000 cases of CFS per million people.
The Centres for Disease Control and Prevention (CDC) states that individuals of any age, ethnicity or gender can develop CFS but the condition is more common in men than women, in people aged 40 to 60 years and in adults as opposed to children or adolescents. People with a family member who has had the condition are also more likely to develop CFS. There is no evidence to support the theory that CFS is contagious.
The CDC estimates that over 1 million Americans have this condition and nearly 80% of these individuals are undiagnosed. According to the National Health Service, around 250,000 people in the UK have CFS.
Although people of any ethnicity or race may be affected by CFS, those from low income societies are more likely to be affected. A meta-analysis carried out in 2009 demonstrated that African Americans and Native Americans are significantly more likely to develop CFS than White Americans.
Another challenge in identifying and diagnosing cases of CFS is the presence of co-morbidity that shares symptoms with CFS. Examples include fibromyalgia, temporomandibular joint disorder, irritable bowel syndrome, interstitial cystitis, migraine, thyroid disorder, Raynaud’s phenomenon and depression.
Children and adolescents who develop the condition may find symptoms improve with age but adults often do not return to being as healthy as they were before the illness, which may also recur several years after remission. There is a high risk of progressive end-organ damage that may lead to death or even suicide.