Sex differences in myalgic encephalomyelitis and chronic fatigue syndrome

ME/CFS affects four times as many females as males. Sex differences have been found in the pathophysiology of ME/CFS.

Epidemiology
Numerous studies have found the rates of ME/CFS to be substantially higher in adult women than in men, with estimates ranging from 75-85%.

A higher preponderance of women has also been noted in numerous outbreaks including Los Angeles, Akureyri, Rockville, MD, Royal Free Hospital, and Punta Gorda, Florida. In some cases, this was thought to do with the occupational hazard of nursing, but this female-skewed sex ratio was also found in several outbreaks among the general population. However, in other outbreaks, including the 1949-1953 Adelaide outbreak and an outbreak in northern England in 1955, a 1:1 gender ratio was reported. In Akureyri, a significantly higher incidence rate was found among adult women but not in patients under twenty.

A 2015 epidemiology study of ME/CFS in Spain found that although the most common trigger for both males and females was infection, the mean age of symptoms onset was lower in males than females. Males reported less pain and fewer comorbidities. In this cohort, fibromyalgia was present in 29% of the males vs 58% in the females.

Physiology
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.

Notable studies

 * 2015, Gender Differences in Chronic Fatigue Syndrome (Full Text)
 * 2002, Women's experiences of stigma in relation to chronic fatigue syndrome and fibromyalgia.