Overview of Chronic Fatigue Syndrome

Chronic fatigue syndrome (CFS), also called chronic fatigue immune dysfunction syndrome (CFIDS), is a complex disorder that causes severe fatigue that worsens with activity and does not improve with rest. In most cases, patients who have CFS cannot maintain the same level of activity as before they developed the condition.

In addition to fatigue, chronic fatigue syndrome may cause other general symptoms such as muscle weakness and pain, insomnia, and impaired mental abilities (e.g., difficulty concentrating, memory loss).

In 1994, international experts in chronic fatigue syndrome developed the following two criteria for defining the condition:

  1. Severe, chronic fatigue for six (6) months or longer, with other medical conditions excluded through clinical diagnosis.
  2. At the same time, at least four (4) of these symptoms: sore throat; tender lymph nodes; muscle pain; multi-joint pain without swelling or redness; headaches of a new type, pattern or severity; unrefreshing sleep; and malaise (feeling unwell) after activity that lasts more than 24 hours. These symptoms must not have occurred before chronic fatigue and also must have persisted or recurred for at least 6 months.

Incidence & Prevalence of Chronic Fatigue Syndrome

According to the Centers for Disease Control and Prevention (CDC), chronic fatigue syndrome is most common in women between the ages of 40 and 60. CHF, which occurs throughout the world, in all races and ethnicities, affects women 4 times more often than men. The condition can develop at any age, and occurs more often in adolescents than in younger children.

Causes & Risk Factors for Chronic Fatigue Syndrome

The cause of chronic fatigue syndrome is unknown. According to the National Institutes of Health (NIH), studies have shown that chronic fatigue syndrome may result from an abnormal immune system response that causes inflammation within the nervous system. In some cases, the disease may be triggered by the combination of an inadequate immune system and a virus. Physical trauma (e.g., surgery) may also trigger CFS.

Risk factors include the following:

  • Age (more common between the ages of 40 and 60)
  • Gender (more common in women than men)
  • Genetic (familial patterns suggest the disorder may be inherited, but this has not been proven)
  • Prior history of illness
  • Stress

Signs & Symptoms of Chronic Fatigue Syndrome

Symptoms of chronic fatigue syndrome vary and often last for years. In most cases, the condition has a significant impact on daily life. The primary symptom is severe fatigue that persists for at least 6 months. This fatigue often is incapacitating, worsens with activity, and does not improve with rest.

In some cases, CFS symptoms worsen for a period of time (called relapse) and then improve for a period of time (called remission). Evidence suggests that overdoing activity during remission can sometimes cause a relapse, making CFS difficult to manage for many patients.

Other common symptoms of CFS include the following:

  • Difficulty concentrating
  • Fever
  • Headaches(new type, pattern or severity)
  • Joint pain without swelling or redness
  • Malaise (generally feeling unwell) after activity, lasting longer than 24 hours
  • Memory loss
  • Muscle pain
  • Sleep disturbances and unrefreshing sleep
  • Sore throat
  • Tender lymph nodes

Chronic Fatigue Syndrome Diagnosis

To diagnose chronic fatigue syndrome in patients who meet the diagnostic criteria for the condition, other diseases must be ruled out. A medical history can be used to determine if the patient meets the following criteria:

  1. Severe, chronic fatigue for six (6) months or longer, with other medical conditions excluded through clinical diagnosis.
  2. At the same time, at least four (4) of these symptoms: sore throat; tender lymph nodes; muscle pain; multi-joint pain without swelling or redness; headaches of a new type, pattern or severity; unrefreshing sleep; and malaise (feeling unwell) after activity that lasts more than 24 hours. These symptoms must not have occurred before chronic fatigue and also must have persisted or recurred for at least 6 months.

A thorough physical examination is performed to detect other symptoms of CFS, such as fever and swollen lymph nodes. Laboratory tests that may be used to rule out other conditions include blood tests (e.g., white blood cell count) and imaging tests (e.g., magnetic resonance imaging [MRI scan]).

Diseases and conditions that must be ruled out include the following:

  • Autoimmune disorders (e.g., lupus)
  • Cancer
  • Drug dependence
  • Fatigue related to psychological factors alone (e.g., depression)
  • Heart, kidney, or liver disease
  • Hypothyroidism
  • Infection
  • Muscle or nerve diseases (e.g., multiple sclerosis [MS])

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 30 Sep 2006

Last Modified: 06 Nov 2014