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Summary -The spectrum of fatigue states - What is CFS? - What other names are commonly used for CFS? - How common is CFS? - Who is at risk of CFS? - What is the cost of CFS to the community? - Box 1.1
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The spectrum of fatigue states |
Prolonged and disabling fatigue is present in 10%-25% of patients
presenting to general practitioners (Kroenke et al. 1988; David et
al. 1990; Cathebras et al. 1992; Katerndahl, 1993; Walker et al. 1993;
Fuhrer and Wessely, 1995; Hickie et al. 1996a). Fatigue
syndromes lie along a continuum of severity (David et al. 1990; Lewis
and Wessely, 1992; Pawlikowska et al. 1994; Hickie et al. 1995a) from
the ubiquitous transient and mild states to the more severe and
prolonged fatigue disorders, including CFS. As with other problems
in clinical medicine (such as hypertension or obesity) there is a
continuum from health to severe illness, and the challenge is to
identify the point at which the state (of blood pressure, bodyweight,
or fatigue) becomes a source of ill health. In relation to fatigue
states, it is important to identify those people in whom the disorder
is associated with ongoing disability (Komaroff et al. 1996a
; Buchwald et al. 1996) and significant personal or economic cost
(Lloyd and Pender, 1992).
Syndromal diagnoses like CFS are widely used in clinical medicine (e.g. migraine headache, systemic lupus erythematosus, major depression). CFS is not a "disease", as this concept refers to a disorder classified according to its underlying cause or pathophysiology (Jennings 1986). By contrast, CFS is an "illness", which is a subjective state, and can only be defined by reference to the sick individual (Cassell 1991). "Disability" arises when illness interferes with the individual's ability to function normally. People with CFS are clearly ill, and are often significantly disabled, even though the underlying disease process has not been identified. Our goal as physicians is not only to identify and treat disease, but also to help relieve suffering and disability, whatever the cause. | |
What is CFS? |
In 1988, the US Centers for Disease Control proposed the term "chronic
fatigue syndrome" to describe a clinical condition defined by a
cluster of constitutional and neuropsychiatric symptoms occurring
in a distinctive pattern (Holmes et al. 1988). Current diagnostic
criteria (see Box 1) describe CFS as a syndrome of physical and
mental fatigue, usually of acute onset, which is markedly
exacerbated by physical activity. The other common symptoms include
general malaise, headaches, poor memory and concentration,
unrefreshing sleep, myalgia, arthralgia, and irritable mood (Lloyd
et al. 1988b; Hickie et al. 1990; Komaroff and Buchwald, 1991; Hickie et
al. 1995b; Komaroff et al. 1996b). The diagnostic criteria
also emphasise that the person must have been unwell for more than six
months and that the symptom complex is associated with substantial
disability.
In primary care, about two-thirds of people with chronic fatigue will have another medical or psychiatric disorder that accounts for it (Manu et al. 1988a, 1988b, 1989; Buchwald et al. 1995; Lawrie et al. 1997). CFS is not simply a diagnosis of exclusion, although the careful assessment of other possible medical and psychological causes is a fundamental step (Fukuda et al. 1994). Some people with severe fatigue syndromes will fail to meet the research diagnostic criteria for CFS but may still benefit from the assessment and intervention strategies described in these guidelines. Delineating a clinical syndrome facilitates research that tests the validity of the concept by clinical description, laboratory and epidemiological studies. It also encourages pathophysiological and treatment research before the pathogenic process has been clearly elucidated. Although a variety of clinical and research definitions have been proposed (Lloyd et al. 1988b; Holmes et al. 1988; Lloyd et al. 1990; Sharpe et al. 1991; Schluederberg et al. 1992; Fukuda et al. 1994; Komaroff et al. 1996b), the current international consensus criteria for CFS (Fukuda et al. 1994) are generally accepted within the scientific literature. Box 1.1 outlines the criteria for CFS and also for prolonged fatigue and chronic fatigue. | |
What other names are commonly used for CFS? |
In the British medical and patient literature "myalgic
encephalomyelitis" (Lancet 1956), and in the more recent
American patient literature "chronic fatigue and immune
dysfunction syndrome" (CFIDS) have been used to describe the
disorder. Both names inappropriately suggest that the cause is
already understood (inflammation of the brain and muscles, or immune
deficiency). Most research groups prefer the term "CFS" as it leaves
open the question of aetiology (Holmes et al. 1988; Fukuda et al.
1994).
Neurasthenia (literally meaning "nervous exhaustion") is a diagnosis included in the International Classification of Diseases (10th Edition) to describe a syndrome of mental and physical fatigue of at least three months' duration (ICD-10). The term has a long tradition in psychiatric classification (Wessely, 1990; Hickie et al. 1997), although its specific relationships with CFS, and common psychological disorders (anxiety and depression), are not resolved. Neurasthenia has a prevalence of 5.4% (range, 2%-10%) in primary care settings worldwide (Goldberg and Lecrubier, 1995). | |
How common is CFS? |
The reported prevalence estimates of CFS differ as a consequence of
variations in sampling methods, survey instruments and diagnostic
criteria, particularly with regard to duration of illness and the
extent to which alternative medical and psychiatric diagnoses were
excluded (Box 1.1). Early attempts to record the community
prevalence suggested a range of 0.002% to 0.04% (Lloyd et al. 1990;
Price et al. 1992; Gunn et al. 1993). These figures appear to be
substantial underestimates as a consequence of limitations in
sampling or diagnostic protocols.
The true prevalence of CFS can only be determined in large scale community studies employing adequate case detection and characterisation techniques. To date, three studies have provided a more realistic estimate of 0.2% to 0.7% (that is, 200-700 cases per 100,000 persons: Jason et al. 1995; Buchwald et al. 1995; Lawrie et al. 1997). Further studies are now required. In primary care settings, estimates of the prevalence of CFS are between 0.5% and 2.5%, depending on the intensity of medical, psychiatric and laboratory evaluation (Box 1.1). While physicians working in tertiary referral centres may encounter patients with CFS quite commonly, primary care doctors will not (Box 1.1). Preliminary estimates of the incidence of new cases per year of prolonged fatigue or chronic fatigue in primary care are 3%-5% (Wessely et al. 1995b; Hickie et al. 1996b; Lawrie et al. 1997), whereas the incidence of CFS is about 0.4% (Lawrie et al. 1997). | |
Who is at risk of CFS? |
CFS predominantly affects young adults, with a peak age of onset
between 20 and 40 years (Lloyd et al. 1990; Jason et al. 1995; Lawrie et
al. 1997). In study samples from treatment centres CFS appears to be
more common in women (typically in a ratio of 2-3:1 -- Lloyd et al. 1989;
Komaroff 1994), but this may be because women attend all levels of
medical care more frequently than men (Henderson 1974). CFS does not
preferentially affect individuals from upper socioeconomic groups
(contrary to the notion of "yuppie flu" -- Lloyd et al. 1990), rather,
some studies suggest that fatigue syndromes may be more common in
people from more socially disadvantaged groups (Hickie et al. 1996a; Lawrie et al. 1997).
It is unlikely that common, non-specific viral illnesses trigger the onset of CFS, but specific infections, such as mononucleosis, quite commonly do so. A large controlled study in general practice (Wessely et al. 1995b) found that people presenting with minor symptomatic infections were no more likely to report chronic fatigue subsequently than those presenting for other reasons. By contrast, a prospective cohort study following individuals with serologically confirmed Epstein-Barr virus infection documented the development of a chronic fatigue state that was independent of psychiatric diagnoses (White et al. 1995b). In the Australian context it appears that infections such as Q fever and Ross River virus infection may also trigger CFS (Marmion et al. 1996; Ayres et al. 1996; Selden and Cameron, 1996; reviewed in Hickie et al. 1996c ). | |
What is the cost of CFS |
The financial impact of CFS on people with CFS and the community has
been evaluated (Lloyd and Pender 1992). A conservative Australian
estimate of the direct costs (those incurred in diagnosis and
management) was $1936 per case per annum (in 1988/89 dollars). After
inclusion of indirect costs (those related to lost productivity
associated with the disorder) the aggregate annual cost of CFS was
$9436 per case (1988/89 dollars). Converting these costs to 1997
dollars gives a direct cost of $2509 per case and an annual aggregate
cost of $12 228 to the community. Based upon a conservative assumption
of a community prevalence of CFS of 0.2% (200 cases per 100 000
population), this implies an annual cost to the Australian community
of $416 million dollars.
| Next... | Part 2: How should people with fatigue be evaluated? |
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