Epidemiology of myalgic encephalomyelitis and chronic fatigue syndrome

Incidence
Estimates of the prevalence vary widely, owing in part to the variety of definitions used. Estimates range from 0.025% to 0.3% of the population.

In the US, it affects 836,000 to 2.5 million people.

In Australia, up to 242,000 people have CFS (including 94,000 with ME which is a narrower definition).

In 1999, a community-based study by Dr Leonard Jason, et al, performed in the Chicago area found that:
 * CFS was substantially higher among women than men,
 * individuals who identified as people of color exhibited higher rates of CFS than whites, with Latino participants demonstrating the highest CFS prevalence,
 * individuals in the 40- to 49-year-old age range exhibited the highest rates of CFS,
 * the prevalence of CFS was highest among skilled workers and lowest among professionals.

Severity


People with ME/CFS are more disabled and socially marginalized than for most other chronic illnesses.

Around 25 per cent of people with ME/CFS will have a mild form and be able to get to school or work either part-time or full-time, while reducing other activities. About 50 per cent will have a moderate to severe form of ME/CFS and not be able to get to school or work. Another 25 per cent will experience severe ME/CFS and have to stay at home or in bed.

In the US, 50-75% of patients with ME/CFS cannot work.

Gender
Various studies have estimated that 70-80% are women.

Naviaux found women with ME/CFS, but not men, generally had disturbed fatty acid and endocannabinoid metabolism. Men, but not women, generally showed increased serine and threonine concentrations.

Age
A study in Norway found two age peaks, one between 10 and 19 years and a second peak between 30 and 39 years.

Genetics
See also: Genetics of chronic fatigue syndrome

5% of children of mothers with ME/CFS later developed the illness.

Prognosis
On average, many people with ME/CFS will improve in the first five years, but others may mainly stay at home or in bed, or may suffer relapses throughout their lives.

Mortality
One study found no increased risk of all cause mortality or mortality from cancer but an increased risk of suicide. Suicide risk was increased 6.85 compared to the general population. It was based on a cohort that used multiple clinical criteria, including the Oxford criteria. A Spanish study found a suicide risk of 12.75% versus 2.3% in the general population.