Chronic Fatigue Syndrome (CFS) was originally defined in 1988 when the Center for Disease Control (CDC) in the US brought together a number of researchers who had been investigating a strange syndrome characterized by overwhelming fatigue. This definition however was reviewed by a panel of international experts in 1994 and subsequently revised.
CFS is very difficult to diagnose because the main symptom of fatigue is present in so many other illnesses. However, once other illnesses have been ruled out through laboratory tests and physical examination, a diagnosis of CFS may be given if the following criteria are met:
- Clinically evaluated, unexplained persistent or relapsing chronic fatigue that is of new or definite onset (i.e., not lifelong), is not the result of ongoing exertion, is not substantially alleviated by rest, and results in substantial reduction in previous levels of occupational, educational, social, or personal activities.
- The concurrent occurrence of four or more of the following symptoms: substantial impairment in short-term memory or concentration; 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 post-exertional malaise lasting more than 24 hours. These symptoms must have persisted or recurred during 6 or more consecutive months of illness and must not have predated the fatigue.
The full text of the revised definition can be found at the CDC website: http://www.cdc.gov/ncidod/diseases/cfs/about/definition/index.htm
Chronic Fatigue Syndrome is also known by various other names, most commonly:
- Myalgic Encephalomyelitis/Encephalopathy (M.E.)
- Chronic Fatigue Immune Dysfunction Syndrome (CFIDS)
- Post Viral Fatigue Syndrome (PVFS)
These names were given as they describe certain causes and mechanisms proposed to be involved in the illness.
CFS and ME are by far the most widely used names. Using CFS and ME as synonyms to refer to the same disease is controversial in some quarters however, with ME seen by some as a more serious condition with an identifiable trigger (e.g. viral illness) whereas CFS is diagnosed in the absence of such a trigger based on symptoms alone. Indeed ME has been listed as a physical neurological disease by the World Health Organization (ICD G93.3) (34) since 1969 whilst CFS has received only a brief mention in the most recent versions. However, there is seen to be significant overlap in both symptoms and approaches to treatment so most people, both doctors and patients, tend to use CFS and ME to mean the same thing. Recent efforts, primarily in the US have sought to settle the matter by introducing the term 'ME/CFS' and use of this combined name has gained significant popularity in a short period of time and thus will be used for the remainder of this overview.
Symptoms and General Information
Obviously, as is implied by the various names, fatigue is the major symptom in ME/CFS. People often have the misconception that this is the only symptom and hence they assume that sufferers simply like to complain about the normal tiredness that everyone experiences after a day at work etc. ME/CFS is actually much more than fatigue, and the fatigue experienced is a lot more severe than simple tiredness. The following is a list of the major symptoms of ME/CFS.
- Fatigue - This can be both physical and mental fatigue. It is a pronounced fatigue that leads to a significant reduction in ability to carry out normal tasks and live your usual lifestyle. The fatigue is usually ever present to some degree and is not relieved by sleep; in fact it may be a lot worse upon waking, especially after a lot of activity the previous day.
- Exercise Intolerance - A major feature shared by ME/CFS sufferers is the lack of exercise tolerance. Although they may feel reasonably good before exercise, shortly after commencing they feel absolutely exhausted and cannot continue. It is the same thing a marathon runner experiences and is commonly known as "hitting the wall". This phenomenon occurs because the body's cells requirement for oxygen exceeds the supply so they switch to anaerobic (without oxygen) respiration and lactic acid builds up in the muscles.
- Severe Malaise - A general feeling of being ill. It can be described as a "flu-like" or "hangover" feeling.
- Muscle and Joint Aches - These can occur anywhere in the body but the most common sites are the lower back and legs. The aching can be severe and is aggravated substantially by any exertion, physical or mental. There is significant overlap here with Fibromyalgia and many patients are diagnosed with both ME/CFS and Fibromyalgia.
- Cognitive Dysfunction - Symptoms of cognitive dysfunction are a prominent problem in ME/CFS. They include poor concentration, memory loss (constantly forgetting simple information like names and numbers), inability to take in information (having to read the same thing over and over) and a general reduction in cognitive ability and IQ.
- Chronic Headache - As would be expected in someone who feels "ill all over" and achy in general, headaches are a common complaint in ME/CFS. They are different to headaches experienced before the onset of ME/CFS and their severity usually varies inline with other aches and symptoms.
- Balance Disturbance - An unusual but common symptom is a loss of balance or sensation of dizziness. This most often occurs upon standing up and the sufferer may feel faint and even black out. This is often referred to as 'Neurally Mediated Hypotension (NMH)' or 'Orthostatic Intolerance' and is most likely due to low blood pressure or abnormal blood flow to the brain.
- Recurrent Sore Throat - A persistent sore throat and/or swollen glands commonly precedes the onset of ME/CFS and may continue as the illness progresses. This is felt to be an indicator that a viral infection plays a major role in cause of the illness.
- Mood and Sleep Disturbances - Depression, anxiety and irritability are often present which frequently leads to misdiagnosis by doctors. Sleep disturbances are common and may present as hypersomnolence (sleeping more than normal), sleep reversal i.e. sleeping all day and awake at night, or insomnia (inability to sleep). Sleep apnea and Restless Leg Syndrome (RLS) are also common..
- Abdominal Pain/Digestive Disturbances - These are symptoms similar to Irritable Bowel Syndrome and, as with Fibromyalgia, ME/CFS sufferers are often diagnosed with IBS.
- Nausea Particularly apparent when other symptoms feeling particularly ill in general.
- Heightened Sensitivity to Light and/or Sound - Normal everyday levels of sound and light can seem overwhelming to a ME/CFS sufferer. A busy place like a large shop will leave a sufferer totally exhausted very rapidly.
- Visual Disturbances - These may include a blurring of vision, especially when reading, and eye pain.
- Skin Sensitivity - This is another unusual symptom. Some ME/CFS sufferers experience a sensation where patches of skin become very sensitive to touch and may feel like they are burning. Some people describe this as a "crawling sensation".
The number and severity of symptoms varies drastically between individuals but the symptoms of fatigue, malaise, cognitive dysfunction and possibly muscle aches, are the core symptoms of the illness.
An important thing to note is that all symptoms are generally made a lot worse by physical or mental exertion of any kind. It is common for the severity of the illness to wax and wane from day to day as well as over longer periods of weeks and months. Patients frequently experience periods of remission and relapse.
Subtypes of ME/CFS
In the first half of 2008 a team led by prominent ME/CFS researcher Dr. Jonathan Kerr published the results of a genetic study which identified 7 different subtypes of the condition. The study involved 55 ME/CFS patients from both the US and UK along with 75 healthy controls. Blood samples were taken from all participants and genetic analyses carried out. The results of which, along with information about symptoms provided by patients, led to the discovery of the following subtypes of ME/CFS:
Type 1 - high levels of depression and anxiety as well as poor sleep and high degrees of pain.
Type 2 - severe post-exertional fatigue, joint and muscle pains.
Type 3 - mildest form of the disease.
Type 4 - moderate levels of body pain and sleep problems
Type 5 - most severe muscle weakness and predominance of gut problems
Type 6 - associated with significant fatigue
Type 7 - most severe form with high levels of pain, swollen glands and headaches.
It was found that types four and six were the most common forms of the condition.
More information on the ME/CFS subtypes research
The cause, or causes of ME/CFS are still not clear. There are a number of theories that have been proposed, the main ones propose the following factors as the cause or causes of the illness:
- Viral Infection
- Mycoplasma Infection
- Immune or Endocrine Dysfunction
- Autonomic Nervous System Dysfunction
- Environmental Toxins
- Genetic Factors
- Candida Overgrowth/Gut Dysbiosis
- Heavy Metal Sensitivity
- Emotional Stress or Trauma
For a long time it was thought that chronic Epstein Barr Virus (EBV) infection was the sole cause of ME/CFS but this theory has lost support as research has shown ME/CFS to be a much more complex illness. Recent studies are still finding a link to EBV however, at least in a subset of patients (1). There are studies ongoing into other possible viral causes, Human Herpes Virus 6 (HHV-6) has often been detected in the blood of ME/CFS patients and has attracted a lot of attention in the past but some recent studies have failed to find a link (2, 3). Most recently two papers from seperate researchers were published in the Journal of Clinical Pathology in September 2007 indicating that ME/CFS is associated with chronic enterovirus infection of the stomach (32, 33). Researchers believe this may account for many of the gastrointestinal symptoms experienced by ME/CFS sufferers.
Despite inconclusive research findings with respect to specific viral causes for ME/CFS, it is still thought by many that a dysfunctional immune response to viruses and chronic viral infections are at the heart of the condition. One key piece of evidence for this position comes from the finding that ME/CFS patients have abnormalities of RNase L. RNase L is an enzyme found in every cell in the body which is activated within a particular cell when it comes under attack from viruses, and to a lesser extent bacteria and some toxins. The job of RNase L is to take care of the threat from invading viruses by destroying their RNA or by signaling an already infected cell to die (apoptosis), taking the virus with it. It has been found in numerous studies that ME/CFS patients have fragmented RNase L and the RNase L system as a whole is dysfunctional. As a result the patient has compromised defences against viral infection. The RNase L abnormalities are seen as the closest thing to a biomarker for ME/CFS currently available as the findings are so consistent (31).
Another piece of evidence that links ME/CFS to a viral cause, or at least the involvement of a virus, is the discovery that 67% of patients tested by the Whittemore Peterson Institute (WPI) in Nevada, USA, tested positive for a retrovirus (a virus similar to HIV) known as xenotropic murine leukemia virus-related virus (XMRV) (35). The discovery of such a large number of ME/CFS patients being positive XMRV has been seen as a significant finding and generated substantial attention from both the press and medical organisations. At the time of writing furthr studies are required to elucidate the role (if any) of XMRV in ME/CFS.
There is substantial evidence for mycoplasma infection playing a role in ME/CFS. Mycoplasma can be defined as the smallest organisms lacking cell walls that are capable of self-replication and can cause various diseases in humans. Although usually associated with respiratory and urinary disease, mycoplasma are thought by a growing number of medical professionals to be responsible for a number of unexplained symptoms, especially chronic fatigue states. Mycoplasma fermentans has been found in the blood of ME/CFS patients at a much higher rate than in the overall population.
In an article entitled 'Scientific Facts Versus Fiction About Mycoplasma', Aristo Vojdani, Ph.D., M.T. (30) describes recent findings about Mycoplasma fermentans:
"Although mycoplasmas are recognized primarily as extracellular parasites or pathogens of mucosal surfaces, recent evidence suggests that certain species may invade the host cells.
The molecular and cellular bases for the invasion of M. fermentans from mucosal cells to the bloodstream and its colonization of blood remain unknown.
Also, it remains unclear whether M. fermentans infection of white blood cells is transient, intermittent or persistent. It is not clear how these stages influence any disease progression. The invasion of host blood cells by M. fermentans is due to inhibition of phagocytosis by a variety of mechanisms, including antiphagocytic proteins such as proteases, phospholipases and by oxygen radicals produced by mycoplasmas."
ME/CFS has long been considered to be an illness of immune dysfunction and there is ample evidence that considerable immune dysfunction is present in patients. Immune activation is a global finding with a range of specific abnormalities present in significant numbers of patients. The most common of these include elevated T lymphocyte numbers and elevated circulating cytokines (immune signaling chemicals). Despite this, immune cell function of ME/CFS patients is poor, with low natural killer cell cytotoxicity (NKCC), poor lymphocyte response to mitogens in culture, and frequent immunoglobulin deficiencies, most often IgG1 and IgG3 (4). Another finding is that the immune system of ME/CFS patients is unbalanced, with T-helper cells of type 2 heavily outnumbering those of type 1 (5). Th1 cells stimulate immunity directed at organisms which invade cells, such as viruses whereas Th2 cells stimulate immunity targeted towards invaders found outside of cells such as bacteria, parasites, toxins and allergens. This finding could certainly explain the fact that ME/CFS sufferers have a higher occurrence of allergies than the healthy population. It also provides a reason why ME/CFS patients may have chronic viral infections as immunity is directed away from protecting against them.
Much research has centred around the endocrine system of ME/CFS patients. Particular interest has been paid to the hypothalamic-pituitary-adrenal (HPA) axis which is responsible for the stress response. A number of abnormalities have been observed in ME/CFS patients with regards to this including low cortisol and DHEA sulphate levels as well as altered melatonin metabolism (6). Cortisol and DHEA-S work in synergy to control how the body reacts to stress. Low levels affect your ability to deal with stress and can cause fatigue, low blood pressure, hypoglycemia, poor brain function and a number of other problems common to ME/CFS sufferers. Melatonin is a hormone whose main action appears to be to induce sleep. During the day the pineal gland, stimulated by light signals the body to produce serotonin and other chemicals to 'wake the body up'. When light levels fall the pineal gland signals the production of melatonin in place of serotonin, preparing the body for sleep. If melatonin production is disturbed as it has been seen to be in ME/CFS then this can cause disruption to sleep as is commonly seen in ME/CFS patients. Adding weight to this hypothesis is the fact that low doses of hydrocortisone (cortisol) have been shown to improve symptoms in a number of studies (7, 8). Many physicians also prescribe DHEA and melatonin in low doses for their patients and many find that they are of great benefit.
Autonomic Nervous System Dysfunction
One common problem in ME/CFS that is often overlooked is a feeling of dizziness, weakness and feeling lightheaded upon standing. Studies have confirmed that a majority of ME/CFS patients have what is known as neurally mediated hypotension (NMH) (9,10). This means that when ME/CFS patients stand up or exert themselves (especially walking up hills or climbing stairs) their blood pressure can drop dramatically. When a healthy person carries out these activities the autonomic nervous system automatically increases output of adrenal hormones (corticosteroids, adrenalin etc) which in turn cause the heart to pump harder and blood pressure to increase. In ME/CFS this often doesn't happen correctly so there is a lack of bloodflow to the head and the symptons described above result. Researchers and doctors are now trying to treat NMH in ME/CFS patients where it is identified. Research has centred around administering small doses of corticosteroids to provide the body with the amount it should be producing by itself. Results so far have not been favourable but research in this area is ongoing (11, 12). Despite the failure of these studies to see an improvement using low dose corticosteroids a number of doctors specializing in ME/CFS are adament that this treatment benefits a subset of their patients where definate NMH is present. Many doctors treating ME/CFS also recommend dramatically increasing salt and water intake to help increase blood presure and reduce NMH related symptoms.
Both ME/CFS and fibromyalgia patients suffer from strange cognitive difficulties. Often feeling overwhelmed by sounds, smells and other sensory information, especially when in busy public places such as a mall or office. Skin often feels very sensitive to the touch as well. Dr. Jay Goldstein believes these and the other symptoms of ME/CFS can be explained by neurological dysfunction. When the brain receives sensory information such as this, the prefrontal cortex decides on the importance of the information before passing it on to the rest of the brain for processing. In ME/CFS sensory information that should be classified as low importance is given high importance. As a result, the brain is overwhelmed by all this "important" information all at once and the patient feels overwhelmed and exhausted. At the root of this information processing problem may be deficiency of certain neurotransmitters, most importantly glutamate, norepinephrine and dopamine.
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There is a large proportion of ME/CFS patients who complain of everyday amounts of volatile chemicals triggering or worsening symptoms, i.e. multiple chemical sensitivity (MCS). This has led some researchers to look down this path for answers to the CFS puzzle. One study quotes the rate of severe chemical sensitivity amongst ME/CFS patients at 20%-47% (13). The same study provides compelling evidence that the limbic system (the emotional centre of the brain) of susceptible individuals can become sensitized by chemical, biological and psychological mechanisms and that subsequent exposure to stimuli can cause disregulation of multiple body systems including behavioral, autonomic, endocrine, and immune system functions. Animal models have shown that sensitization can occur as a result of chronic exposure to everyday amounts of volatile organic chemicals (VOC's). In addition to these findings there is also strong evidence of abnormalities of detoxification in ME/CFS. Glutathione, the body's most powerful antioxidant, is consistently found to be low (14, 15). Glutathione may become depleted due to chronic exposure to high levels of toxins. This could potentially be as a result of exposure to toxins in the air or from chemicals of gut origin in the presence of gut dysbiosis. Overactivation of the immune system also depletes glutathione so this may come as a knock on effect from immune system abnormalities. What is certain is that low glutathione leads to fatigue and muscle weakness and pain due to its role in energy metabolism. Low glutathione also results in oxidative stress, meaning that highly reactive oxygen molecules are not neutralized and are thus free to roam the body damaging cells and interfering with potentially any body system.
Learn more about multiple chemical sensitivity
Genetics can be said to be a factor of varying importance in the development of any illness. Consistent with this statement, a number of possible areas of genetic susceptibility have been identified for ME/CFS in various studies. One such study involving twins with ME/CFS and healthy control twins found that the ME/CFS group had much slower reaction times on all speed related cognitive tests. The researchers postulated that this indicated a central information processing deficit in the brain (16). This finding illustrates one theory about the pathogenesis of ME/CFS best described by Dr. J. Goldstein. Dr. Goldstein has treated thousands of ME/CFS patients based on his theory that their brains process sensory information abnormally as a result of certain neurochemical deficiencies. Other research, also centered around brain function, found that ME/CFS patients have differences in genes responsible for serotonin production which leads to lower reservoirs of serotonin, the chemical responsible for maintaining positive moods and also healthy sleep cycles, amongst other functions (17). Finally, a study again using twins, found evidence of immune dysfunction indicating a possible genetic susceptibility (18).
There have been two genetic studies recently that have been hailed as major advances in understanding chronic fatigue syndrome:
The first hit the headlines in July 2005. It suggests that gene expression, the pattern in which genes are switched on and off' is significantly different for certain genes in those with ME/CFS. Researchers at Imperial College, London, looked at the way genes are activated in immune cells of 25 ME/CFS patients and 25 healthy controls. They initially found 35 genes that showed differences while more precise examination revealed 16 that showed definite and significant abnormalities. The lead researcher, Dr Jonathon Kerr suggests that the results support the theory that the illness is often triggered by a virus, namely those discussed previously on this page. Many of the genes that were identified affect the functioning of the mitochondria, the energy generating plants within cells. As such, the abnormal gene expression could account for symptoms of fatigue and lack of energy. The energy producing mitochondria within patients cells may literally be not producing enough energy. The team behind the research hopes to run a much larger study of 1000 patients in the future and it is hoped the research will lead to reliable diagnostic tests for ME/CFS and to new treatment approaches.
The second study, the largest ever to focus on ME/CFS, was completed in 2006 and provided the results that the ME/CFS community has been waiting for . Dr. Julie Gerberding, director of the Centers for Disease Control (CDC) said at a press briefing It really is the first credible evidence of a biological basis for chronic fatigue syndrome. The study involved 227 ME/CFS patients and was conducted in Wichita, Kansas at a cost of $2 million. The study volunteers spent two days in hospital undergoing detailed clinical evaluations including sleep studies, cognitive functioning measurements, autonomic nervous system evaluations, extensive blood work and genetic testing. The activity levels of 20,000 genes were assessed and it is here where the really groundbreaking findings were discovered. At the press briefing, Dr. Reeves, the lead ME/CFS researcher at the CDC, stated For the first time ever, we have documented that people with ME/CFS have certain genes that are related to those parts of brain activity that mediate the stress response. And that they have different gene activity levels that are related to their bodys ability to adapt to challenges and stresses that occur throughout life, such as infections, injury, trauma or various adverse events. What this means is that people with chronic fatigue syndrome generally have a lower tolerance to these various stressors. The result of this is that in people predisposed to ME/CFS, their bodies can become overwhelmed by events that other people would be able to shrug off, and this is where dysfunction in various body systems such as the nervous, endocrine and immune systems sets in. The researchers at the CDC went on to say that they identified a number of different subgroups within the patients tested, verifying what many had suspected, that ME/CFS isn't a single easily identifiable disease with a single cause and diagnostic marker, but rather the result of a complex disease process. They also stated that this research proves once and for all that ME/CFS is a very real biological disease and hope that it will lead to better diagnosis and treatment in the near future.
Around 30 years ago a handful of physicians, most notably Dr's Crook, Truss and Trowbridge described a syndrome characterized by a wide range of symptoms very similar to those of ME/CFS which they suggested was caused by overgrowth of the normal intestinal yeast such as Candida albicans which proliferated due to antibiotic usage and other factors. They treated their patients with antifungal drugs with reportedly good results. A small amount of subsequent research seems to validate their theories with it becoming clear that antibiotic drugs adversely affect intestinal flora and allow Candida sp. to become prevalent (19, 20). There are studies that appear to show successful treatment of intestinal candidiasis with antifungal drugs as well (21, 22). Strangely, although Dr. Crook in particular connected intestinal yeast overgrowth with ME/CFS decades ago there has been little material published regarding this since, apart from a few papers again suggesting the link due to the observed similarities between supposed yeast related illness and ME/CFS (23). The most likely reason for this is the still pervasive view that there are no definitive tests for intestinal yeast overgrowth. Testing of urine or blood for 'tartaric acid' would appear to offer just this definitive test however. Tartaric acid is a product solely of yeast and is not produced as part of human metabolism, therefore any detected in blood or urine must have originated from the yeast that inhabit the intestinal tract. Studies could, and should, be undertaken to compare tartaric acid levels between healthy controls and patients with ME/CFS. Patients of all the illnesses on this site as well as other unexplained chronic illnesses should also be tested to establish the role of yeast overgrowth in these conditions. An important study recently published has shown the link between antibiotic alteration of gut flora, candida proliferation and the initiation of allergic illness ME/CFS. Since allergies are prevalent amongst ME/CFS sufferers this research is further evidence that the link between ME/CFS and intestinal yeast should be investigated. Despite the lack of published research, all the major diagnostic labs that serve functional/integrative medicine physicians consistently report a correlation between yeast markers such as tartaric acid, elevated blood ethanol and Candida antibodies in samples from ME/CFS patients. A large number of physicians specializing in the treatment of ME/CFS and related illnesses include anti-fungal agents as a major part of their treatment protocols. A search of online forums, chat rooms and blogs also reveals a large number of ME/CFS patients who have had success self-treating with an anti-fungal protocol. Further research in this area is long overdue.
With more published research behind it is the idea that small intestinal bacterial overgrowth (SIBO) might play a role in fibromyalgia (15). This is something that has been extensively connected with irritable bowel syndrome in recent years (26) and as ME/CFS and IBS are commonly diagnosed in the same individual, it offers another avenue of potential treatment. SIBO can be treated with targeted antibiotic drugs or with antibiotic herbs.
Learn more about Candida & gut dysbiosis
'Leaky gut syndrome' is thought to be a result of gut dysbiosis and food allergies, amongst other things, and could contribute to the disease process in ME/CFS and a number of other chronic illnesses.
Learn more about leaky gut syndrome
Heavy Metal Sensitivity
A surprising amount of published research indicates a role for heavy metals as causative agents in ME/CFS. One study using ME/CFS patients and healthy controls found that the ME/CFS group had significantly higher serum levels of aluminium at the expense of iron (27). The researchers correlate this low iron level with low DHEA which has we have previously mentioned as a common finding and possible contributor to symptoms in ME/CFS patients. Another research group found an increased incidence of nickel allergy in ME/CFS patients compared to control subjects. They suggest that immune activation by nickel or cross-reacting metals could be an etiological factor in ME/CFS (28). Mercury amalgam dental fillings are often cited as a possible cause of chronic illnesses and there is published evidence that this may well be the case, although specific research with ME/CFS patients appears to be lacking (29).
It has been suggested that a significantly high proportion of ME/CFS patients have a "Type A" personality. This means they are highly driven people who put a lot of pressure on themselves and need to be the best and first at everything and hate to make any mistakes, basically they are perfectionists. This has led a lot of people to speculate that stress and its effects on the functioning of the brain are at the root of the illness. This theory is strengthened by the evidence discussed above regarding dysfunction of the HPA axis and stress response in ME/CFS sufferers. Stress also has deleterious effects on the immune system so it may be that people with a stress prone personality are more at risk from opportunistic infection or other disease causing factors.
It is clear that there are a large number of abnormalities in multiple body systems in ME/CFS patients. These abnormalities centre around the nervous, endocrine and immune systems and the way these interact with each other. Although these abnormalities have been identified it is still unclear which are causes and which are effects. New research will hopefully shed more light on this but until then doctors who are seeing the best results with patients seem to be those who take a multifactorial approach and try to correct as many of the abnormalities discussed as they possibly can, using currently available treatments.
As there is significant crossover between ME/CFS and fibromyalgia , possible causes of fibromyalgia may well apply to ME/CFS as well. Take a look at our fibromyalgia page.