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Chronic fatigue syndrome (CFS) disproportionately affects women, but has long been under-recognized and under-diagnosed. CFS is now one of the most common chronic illnesses of our time. It is also one of the most misunderstood. Private and government research is shattering many misconceptions, showing chronic fatigue syndrome to be a major public health problem.

A groundbreaking, community-based study of CFS by Dr. Leonard Jason of DePaul University, which was published in the Archives of Internal Medicine, showed a prevalence rate of 422 of every 100,000 Americans. As many as 800,000 people nationwide suffer from CFS, twice the number previously estimated by the Centers for Disease Control and Prevention. (Early CFS epidemiological studies, which were based on physician referrals for case ascertainment, underestimated the prevalence of the illness.)

Even more shocking, the study revealed that only 10 percent of those with chronic fatigue syndrome had been previously diagnosed. Thus, 90 percent of people with the illness are struggling without the benefit of medical diagnosis or treatment.

CFS was found to be more common in women, with 522 females per 100,000 versus 291 males per 100,000. When comparing the prevalence of CFS in women to the prevalence of other diseases, CFS emerges as a serious women's health concern. The prevalence rate for women with CFS is higher than it is for AIDS (12 women per 100,000), breast cancer (26 women per 100,000) and lung cancer (33 women per 100,000). CFS is not limited to any specific race, age or socioeconomic group. Contrary to the "yuppie flu" myth, this study also showed the illness to be wide-spread in low-income and minority communities. It is most common minorities, especially Latinos (726 cases per 100,000), with Latinos and Mexican Americans exhibiting higher rates than Caucasians.

Although there is no known etiology and no known diagnostic marker, there is substantial objective, well-documented evidence of central nervous system, (CNS), immune, endocrine, cardiovascular, and autonomic nervous system abnormalities which indicate that CFS is biologically, not psychologically, determined.

The leading model of CFS pathogenesis is rooted in scientifically identified abnormalities in the brain (central nervous system) and the immune system, both of which affect and alter the function of the other.

A variety of immunologic abnormalities have been reported, especially impaired function of natural killer cells and increased numbers of activated CD8+ T cells. These are consistent with the hypothesis that the immune system is chronically activated in patients with CFS. This immune system activation can cause brain dysfunction via cytokine over-production, which leads to fatigue, cognitive dysfunction, hormonal dysregulation and other features of CFS.

The identified abnormalities mimic the immune pattern of a body fighting a virus, even though no virus has been identified as the cause of CFS. The most intriguing recent immunological finding in CFS is the discovery of a biochemical dysregulation of the 2-5A RNase-L antiviral pathway, a pathway which is also known to be up-regulated in viral infections.

The term chronic fatigue syndrome was introduced in 1988 by the Centers for Disease Control to describe medically unexplained, persistent or relapsing fatigue of new onset. CFS was redefined in 1994 and now has become a broad diagnostic category and selects a heterogeneous (mixed) patient population. It is characterized by at least six months of profound fatigue, with some of the associated symptoms: impaired memory or concentration, sore throat, tender cervical or axillary lymph nodes, muscle pain, multi-joint pain, headaches, unrefreshing sleep, post-exertional weakness.

Symptoms also frequently include vertigo (dizziness), visual disturbances, photophobia, spacial disorientation, disequilibrium, nausea, paresthesias (numbness and tingling), dyspnea, emotional lability (mood swings), tachycardia, sleep disorders (hypersomnia or insomnia), low grade fever, intolerance to alcohol, seizure activity. Initial research suggested that CFS was a relatively rare disorder and affected mainly upper middle class white women.

For some time there were even disputes in medical circles about whether CFS existed or if it was a "real" illness, even though it is formally recognized by the CDC, NIH, SSA, WHO. It was initially disparagingly dubbed "Yuppie flu," giving the impression that it affected mainly whiny overachievers who couldn't handle stress and burned out, which hardly seemed to warrant much attention or concern.

In fact, the name chronic fatigue syndrome itself has caused many of the misconceptions and trivialization of it. Even though fatigue is a prominent feature of many illnesses such as cancer and other serious neurological, infectious and autoimmune diseases, it is a symptom, not an illness. Fatigue is still too vague and imprecise a label since it is a fairly universal experience. It is difficult to convey the severity of an illness whose name denotes tiredness. Patient groups have used the name Chronic Fatigue Immune Dysfunction Syndrome (CFIDS) in order to differentiate it from "chronic fatigue."

Furthermore, the prominent association of fatigue with psychiatric illness, especially depression, has caused many erroneous assumptions and attributions. Patients with CFS may experience emotional lability and psychological distress. However, the prevalence rates of clinically significant depression in patients with CFS are not very different from those reported in other medically ill populations.

Patients have long been aware that the name is not only completely misleading and inadequate, but it also carries a negative stigma with medical professionals and the general public, which has negatively affected government funding and hinders patients' access to medical care and social services. An attribution study done by Dr. Jason validated patients long held claims about the negative impact of the name, which found that the name itself does influence not only people's attitudes and reactions to the illness but also the type and quality of medical care a person is offered.

Myalgic encephalomyelitis (M.E.) is a more specific and appropriate diagnosis than chronic fatigue syndrome, as it describes a specific condition with muscle and neurological symptoms, not only the ubiquitous symptom of fatigue. More specifically, the fatigue in M.E. is exertion related (vs. "tired all the time"), with a significantly prolonged recovery time, and all symptoms can be exacerbated by levels of physical, cognitive, sensory or emotional stress that would have been of no consequence prior to the illness onset. Currently both names/descriptions may be used, or sometimes may be used interchangeably, which has led to a great deal of confusion. Overall CFS is used more frequently in the U.S., while M.E. is still preferred by most of Europe, Canada and Australia.

M.E. is a systemic disease with many systemic features, but characterized primarily by central nervous system dysfunction, of which fatigue, sleep disorders, autonomic dysfunction, cognitive dysfunction, endocrine dysfunction, proprioceptive dysfunction, sensory dysfunction etc. are among the many and varied manifestations. It is also characterized by what may be a marked variation and fluctuation of symptoms, both in occurrence and intensity.

M.E. is a distinctive clinical entity first reported in patients after outbreaks in the UK in the 1950s and was characterized by persistent fatigue, muscle pain (myalgia), symptoms suggestive of CNS dysfunction and significant deterioration of symptoms after physical exertion. It was originally referred to as epidemic neuromyesthenia in the U.S., based on outbreaks beginning in the 1930's that were initially thought to be a form of 'atypical polio.'

M.E. has been formally classified by the World Health Organization as a neurological disorder in the International Classification of Diseases (ICD) since 1969 and remains classified in the current ICD as a neurological disorder (ICD 10. G.93.3 "Diseases of the Nervous System - Other Disorders of the Brain").

Post-viral fatigue syndrome was also used to describe a similar syndrome where patients could clearly trace the onset of their illness back to a viral infection. However, M.E. has also been known to follow other infectious diseases (such as mononucleosis and Lyme disease), post-infective neurologic diseases (such as Guillain-Barré syndrome), immunizations or exposure to neurotoxins (for example, ciguatera fish poisoning).

There is a full spectrum of disease severity, with some patients being mildly affected while others are in wheelchairs or completely bedridden. The clinical outcome of CFS usually takes one of the three courses: recovery/improvement, relapsing/remitting course, and permanent incapacity or progressive deterioration of symptoms. Studies have shown that recovery is uncommon, with only 4% of patients recovering and 39% showing some symptom improvement after four years.

The quality of life may be particularly and uniquely disrupted in CFS and patients have related profound and multiple losses, including loss of jobs, income, relationships, careers, financial security. Activity is reduced to basic survival needs for some patients. Australian researchers found that patients with CFS had more dysfunction than those with multiple sclerosis, and that the degree of impairment is more extreme than in end-stage renal disease and heart disease, and that only in terminally ill cancer and stroke patients was the sickness impact profile (SIP) greater than in CFS. CFS usually affects people in the prime of their life and, consequently, has a significant impact on the nation's productivity. Studies on the burden of disease and cost to society have shown a staggering social and economic impact, based on cost of treatment, loss of earnings and tax revenue and the cost of federal and state benefits.

CFS is a serious and disabling health condition that frequently results in marked interruption of work, family life and social activities; therefore, the illness carries important implications related to public health and policy. New research and developments continue to underscore how important it is that the medical community, policymakers and the public become better educated about this illness.

About the author: Jill McLaughlin is the Executive Director of an association for CFS located in Needham, MA..

Article source: The National Women's Health Information Center (NWHIC) - online at http://www.4woman.gov, is part of the US Department of Health and Human Services' Office on Women's Health.