Chronic Fatigue Syndrome

What is Chronic Fatigue Syndrome?

Chronic fatigue syndrome (CFS) is the most common name The disorder may also be referred to as post-viral fatigue syndrome (PVFS, when the condition arises following a flu-like illness), myalgic encephalomyelitis (ME), or several other terms. The etiology (cause or origin) of CFS is currently unknown and there is no diagnostic laboratory test or biomarker. Symptoms of CFS include widespread muscle and joint pain; cognitive difficulties; chronic, often severe, mental and physical exhaustion; and other characteristic symptoms in a previously healthy and active person. CFS patients may report additional symptoms including muscle weakness, hypersensitivity, orthostatic intolerance, digestive disturbances, depression, poor immune response, and cardiac and respiratory problems. It is unclear if these symptoms represent co-morbid conditions or are produced by an underlying etiology of CFS. All diagnostic criteria require that the symptoms must not be caused by other medical conditions.

CFS is thought to have an incidence of 4 adults per 1,000 in the United States. For unknown reasons CFS occurs most often in people in their 40s and 50s, more often in women than men, and is less prevalent among children and adolescents.

Whereas there is agreement on the genuine threat to health, happiness and productivity posed by CFS, various physicians' groups, researchers and patient advocates promote different nomenclature, diagnostic criteria, etiologic hypotheses and treatments, resulting in controversy about many aspects of the disorder. The name CFS itself is controversial as many patients and advocacy groups, as well as some experts, believe the name chronic fatigue syndrome stigmatizes, by not conveying the seriousness of the illness, and want the name changed.

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Chronic Fatigue Syndrome Symptoms

Onset

The majority of CFS cases start suddenly, An Australian prospective study found that after infection by viral and non-viral pathogens, a sub-set of individuals met the criteria for CFS, with the researchers concluding that "post-infective fatigue syndrome is a valid illness model for investigating one pathophysiological pathway to CFS". However, accurate prevalence and exact roles of infection and stress in the development of CFS are currently unknown. Many significant risk factors for developing CFS are known, but "definitive evidence that would be meaningful for clinicians is lacking".

Symptoms

The most commonly used diagnostic criteria and definition of CFS for research and clinical purposes were published by the United States Centers for Disease Control and Prevention (CDC).

  1. A new onset (not lifelong) of unexplained, persistent fatigue unrelated to exertion and not substantially relieved by rest, that causes a significant reduction in previous activity levels.
  2. Four or more of the following symptoms that last six months or longer:
    • Impaired memory or concentration
    • Post-exertional malaise, where physical or mental exertions bring on "extreme, prolonged exhaustion and sickness"
    • Unrefreshing sleep
    • Muscle pain (myalgia)
    • Pain in multiple joints (arthralgia)
    • Headaches of a new kind or greater severity
    • Sore throat, frequent or recurring
    • Tender lymph nodes (cervical or axillary)

There are no medical tests or physical signs to diagnose CFS, and a reduction in the complexity of activity has been observed, with reported impairment comparable to other fatiguing medical conditions such as late-stage AIDS, lupus, rheumatoid arthritis, chronic obstructive pulmonary disease (COPD), and the effects of chemotherapy. CFS affects a person's functional status and well-being more than major medical conditions such as multiple sclerosis, congestive heart failure, or type II diabetes mellitus The severity of symptoms and disability is the same in both genders with strongly disabling chronic pain, but despite a common diagnosis the functional capacity of individuals with CFS varies greatly. While some lead relatively normal lives, others are totally bed-ridden and unable to care for themselves. Employment rates vary with over half unable to work and nearly two-thirds limited in their work because of their illness. More than half were on disability benefits or temporary sick leave, and less than a fifth worked full-time.

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Chronic Fatigue Syndrome Pathophysiology

The mechanisms and pathogenesis of chronic fatigue syndrome are unknown. infection by viruses and pathogenic bacteria, hypothalamic-pituitary-adrenal axis abnormalities, immune dysfunction as well as psychological and psychosocial factors. Athough it is unclear which factors are a cause, or consequence, of CFS, various models are proposed.

A 2009 study suggests a link between the retrovirus xenotropic murine leukemia virus-related virus (XMRV) and chronic fatigue syndrome. Researchers identified DNA of the virus in the blood of 68 of 101 patients (67%) compared to 8 of 218 (3.7%) of healthy controls, and reported the ability to infect cell cultures in vitro with XMRV from activated cells or plasma derived from CFS patients. A prior claim of retroviral associations with CFS was subsequently negated.

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Chronic Fatigue Syndrome Classification

Notable definitions include:—the most widely used clinical and research description of CFS, The 1994 criteria require the presence of four or more symptoms beyond fatigue, where the 1988 criteria require six to eight.—includes CFS of unknown etiology and a subtype called post-infectious fatigue syndrome (PIFS). Important differences are that the presence of mental fatigue is necessary to fulfill the critera and symptoms are accepted that may suggest a psychiatric disorder.—this definition requires the presence of symptoms from at least one category of autonomic, neuroendocrine, or immune symptoms. An important difference is the Canadian definition excludes patients with symptoms of mental illness.

Using different case definitions may influence the types of patients selected and there is research to suggest subtypes of patients or disease exist. Clinical practice guidelines, with the aim of improving diagnosis, management, and treatment, are generally based on case descriptions. An example is the CFS/ME guideline for the National Health Service in England and Wales, produced in 2007 by the National Institute for Health and Clinical Excellence (NICE).

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Chronic Fatigue Syndrome Treatment

Many patients do not fully recover from CFS even with treatment, and there is no universally effective curative option. Diets, physiotherapy, dietary supplements, antidepressants, pain killers, pacing, and complementary and alternative medicine have been suggested as ways of managing CFS. Cognitive behavioural therapy (CBT) and graded exercise therapy (GET) have shown effectiveness for some patients in multiple randomized controlled trials. As many of the CBT and GET studies required patients to visit a clinic, severely affected patients may have been excluded.

Cognitive behavioral therapy

Cognitive behavioral therapy (CBT), a form of psychological therapy often used to treat chronically ill patients, that is "useful in treating some CFS patients."

A ''Cochrane Review'' meta-analysis of 15 randomized, controlled cognitive behavioral therapy trials with 1043 participants concluded that CBT was an effective treatment to reduce symptoms of fatigue. Comparing CBT with "usual care," four reviewed studies showed that CBT was more effective (40% vs 26%). In three studies, CBT worked better than other types of psychological therapies (48% vs 27%). The effects may diminish after a course of therapy is completed; the reviewers write that "the evidence base at follow-up is limited to a small group of studies with inconsistent findings" and encourage further studies. Another recent meta-analysis finds improvements in randomized controlled trials ranging from 33-73%. A systematic review published in 2006 included the same five RCTs, noting that "no severely affected patients were included in the studies of GET".

Pacing

Pacing is an energy management strategy which encourages behavioral change while acknowledging patient fluctuations in symptom severity and delayed exercise recovery. Patients are advised to set manageable daily activity/exercise goals and balance activity and rest to avoid over-exertion which may worsen symptoms. Those able to function within their individual limits are encouraged to gradually increase activity and exercise levels while maintaining established energy management techniques. The goal is to gradually increase the level of routine functioning of the individual. A small randomised controlled trial concluded that pacing with GET had statistically better results than relaxation/flexibility therapy. A recent survey of 828 people suffering CFS found that pacing was evaluated as useful by 96% of the participants, whereas 79% of the participants who had experienced GET reported this had worsened their health status. Medications thought to have promise in alleviating stress-related disorders include antidepressant and immunomodulatory agents. Many CFS patients are sensitive to medications, particularly sedatives, and some patients report chemical and food sensitivities.

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Chronic Fatigue Syndrome Prognosis

Recovery

A systematic review of 14 studies of the outcome of untreated people with CFS found that "the median full recovery rate was 5% (range 0–31%) and the median proportion of patients who improved during follow-up was 39.5% (range 8–63%). Return to work at follow-up ranged from 8 to 30% in the three studies that considered this outcome." .... "In five studies, a worsening of symptoms during the period of follow-up was reported in between 5 and 20% of patients." A good outcome was associated with less fatigue severity at baseline, a sense of control over symptoms and not attributing illness to a physical cause. Another review found that children have a better prognosis than adults, with 54–94% having recovered by follow-up compared to less than 10% of adults returning to pre-morbid levels of functioning.

According to the CDC, delays in diagnosis and treatment can reduce the chance of improvement.

Deaths

Evidence linking CFS to early deaths is unclear. A systematic review of 14 studies of the outcome of CFS recorded 8 deaths, two were unrelated to CFS, one person died by suicide, and the circumstances of death of the other five were unclear. but another study of a much larger group with a longer follow-up found that mortality rates of individuals with CFS did not differ from the general population of the United States.

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Chronic Fatigue Syndrome Epidemiology

Due to the multiple definitions of CFS, estimates of its prevalence vary widely. Studies in the United States have previously found between 75 and 420 cases of CFS for every 100,000 adults. The CDC states that more than 1 million Americans have CFS and approximately 80% of the cases are undiagnosed. There is no direct evidence that CFS is contagious, though it is seen in members of the same family; this is believed to be a familial or genetic link but more research is required for a definite answer.

Risk factors

A recent systematic review included 11 primary studies that had assessed various demographic, medical, psychological, social and environmental factors to predict the development of CFS/ME, and found many had reported significant associations to CFS.

People with fibromyalgia (FM, or fibromyalgia syndrome, FMS) have muscle pain and sleep disturbances. Fatigue and muscle pain occurs frequently in the initial phase of various hereditary muscle disorders and in several autoimmune, endocrine and metabolic syndromes; and are frequently labelled as CFS or fibromyalgia in the absence of obvious biochemical/metabolic abnormalities and neurological symptoms. Multiple chemical sensitivity, Gulf War syndrome and post-polio syndrome have symptoms similar to those of CFS, and the latter is also theorized to have a common pathophysiology.

A 2006 review found that there was a lack of literature to establish the discriminant validity of undifferentiated somatoform disorder from CFS. The author stated that there is a need for proponents of chronic fatigue syndrome to distinguish it from undifferentiated somatoform disorder. The author also mentioned that the experience of fatigue as exclusively physical and not mental is captured by the definition of somatoform disorder but not CFS. Hysterical diagnoses are not merely diagnoses of exclusion but require criteria to be met on the positive grounds of both primary and secondary gain. Primary depression can be excluded in the differential diagnosis due to the absence of anhedonia and la belle indifference, the variability (lability) of mood, and the presence of sensory phenomena and somatic signs such as ataxia, myoclonus and most importantly, exercise intolerance with paresis, malaise and general deterioration. Feeling depressed is also a commonplace reaction to the losses caused by chronic illness which can in some cases become a comorbid situational depression.

Co-morbidity

Many CFS patients will also have, or appear to have, other medical problems or related diagnoses. Co-morbid fibromyalgia is common, where only patients with fibromyalgia show abnormal pain responses. Fibromyalgia occurs in a large percentage of CFS patients between onset and the second year, and some researchers suggest fibromyalgia and CFS are related. As previously mentioned, many CFS sufferers also experience symptoms of irritable bowel syndrome, temporomandibular joint pain, headache including migraines, and other forms of myalgia. CFS patients have significantly higher rates of current mood disorders than the general population. Compared with the non-fatigued population, male CFS patients are more likely to experience chronic pelvic pain syndrome (CP/CPPS), and female CFS patients are also more likely to experience chronic pelvic pain. CFS is significantly more common in women with endometriosis compared with women in the general USA population.

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