Illness Intrusiveness in Myalgic Encephalomyelitis

 

An exploratory study

 

E. Goudsmit, B. Stouten and S. Howes

 

 

Abstract

This study assessed the relationship between illness intrusiveness, symptoms, disability and depression in patients with myalgic encephalomyelitis (ME). Participants were 16 patients with ME and 8 patients with ME plus co-morbid disorders.

The patients with co-morbid disorders reported greater illness intrusiveness than the patients with ME, but there were no differences between the groups on any other variables. Using data from both groups combined, significant correlations were found between illness intrusiveness on the one hand, and fatigue, cognitive dysfunction, physical functioning and depression, on the other.

ME is a disabling illness which has a major impact on various life domains. Research which assesses a wider range of symptoms may help to increase understanding of this condition and improve patient care.

 

Introduction

Many chronic disorders interfere with an individual’s ability to participate in valued activities, reducing the availability of positive experiences and potentially undermining their emotional well-being and quality of life. To study the disruption of a person’s life caused by a disorder and/or its treatment, Devins and his colleagues introduced the concept of illness intrusiveness (Devins et al, 1983).

The central hypothesis is that illness intrusiveness mediates between the disease and treatment (for example, the frequency and severity of symptoms, the duration and adverse effects of the therapy) and subjective well-being (Devins et al, 1993a; Devins et al, 2006). Psychological and social factors are seen as moderating factors; the same magnitude of illness intrusiveness can produce different levels of well-being or emotional distress depending on factors such as one’s age (Devins et al 1992), the extent to which patients perceive themselves to be stigmatized by the condition (Dancey et al, 2002, Devins et al, 1994) and the presence of stressful life-events (Devins et al, 2006).

According to Devins et al, (2006), illness intrusiveness affects subjective well-being by reducing the person’s ability to participate in valued activities and therefore have access to positive outcomes. However, this relationship may also be influenced by the individual’s sense of control or their belief that they can access positive outcomes, or avoid negative ones.

The hypothesized relationship between illness intrusiveness and subjective well-being is supported by research on a variety of conditions including rheumatoid arthritis (Devins et al, 1992), multiple sclerosis (Devins et al, 1993a), cancer (Bloom et al, 1998; De Groot et al, 2005, Devins et al, 1994, Devins et al, 2006; Schimmer et al, 2001), osteoarthritis (Edworthy et al, 1999), systemic lupus erythematosus (Edworthy et al, 2003) and end-stage renal disease (Devins et al, 1993a). It has also been reported in people with primary or secondary sleep disorders (Devins et al, 1993c; Mucsi et al, 2004), psychological conditions (Anthony et al, 1998; Masellis et al, 2003; Robb et al, 1997), irritable bowel syndrome (Dancey et al, 2002) and following heart, liver and lung transplants (Devins et al, 2001).

In one study on multiple sclerosis, illness intrusiveness was associated with increased levels of depressive symptoms, mood disturbance, and decreased life happiness (Devins et al, 1993b). Similarly, illness intrusiveness correlated with depressive symptoms, after controlling for level of physical disability, in patients with rheumatoid arthritis (Devins et al, 1992).

 

The impact of illness

In contrast to conditions such as diabetes and renal failure, which require ongoing treatment to control the underlying disease, illness intrusiveness in other disorders derives more from the symptoms and physical impairment. As predicted by the theoretical framework, studies have reported significant correlations between the severity of symptoms and illness intrusiveness in breast cancer (Bloom et al, 1998, irritable bowel syndrome (Dancey et al, 2002) and multiple sclerosis (Devins et al, 1993b). Likewise, perceived intrusiveness has been linked with various measures of disability in patients with rheumatoid arthritis (Devins et al, 1992) and multiple sclerosis (Devins et al, 1993b).

In studies which assessed individual symptoms, Devins et al reported modest correlations between fatigue and illness intrusiveness in people with multiple sclerosis (Devins et al, 1993b) and end-stage renal disease (Devins et al, 1990). In the latter, muscle cramps and headaches were associated with greater illness intrusiveness than either symptom alone (Devins et al, 1990b). The view that some symptoms have a greater impact than others is further supported by Masellis et al (2003), who found that obsessive symptoms, but not compulsions, correlated with illness intrusiveness.

In addition to the nature and severity of symptoms, it is also important to consider the potential influence of co-morbid conditions. For example, the presence of sleep disorders was associated with greater illness intrusiveness in patients with end-stage renal disease (Mucsi et al, 2004, Devins et al, 1993c) as well as rheumatoid arthritis and multiple sclerosis (Devins et al, 1993c). Similarly, depression was a significant predictor of illness intrusiveness in people with obsessional-compulsive disorder (Masellis et al, 2003).

One illness where illness intrusiveness has not been assessed is myalgic encephalomyelitis (ME). This condition has been described in the medical literature since the thirties (Gilliam, 1938), and generally follows an unremarkable viral infection. However, instead of the expected recovery, the patient develops a variety of symptoms including fatigue, cramps or twitchings, muscle tenderness and weakness, paraesthesiae, frequency of micturition, blurred vision, hyperacusis, and a general sense of ‘feeling awful’. Following this phase, the multiplicity of symptoms can be divided into three main groups. The most characteristic and dominant symptom of the illness is muscle fatiguability following minimal exertion and a delayed recovery of muscle power after exertion ends (Ramsay, 1988). The prolonged delay in the restoration of muscle strength may range from 24 hours to five days or longer and over-exertion during this time has been implicated as a major cause of relapse (Ramsay, 1983, 1988). Of clinical significance is that the muscle weakness is not general. The disease tends to affect the most often used muscles, so that in right-handed people, the muscles in the right hand and arm are generally weaker than those on the left. The muscle fatiguability and prolonged delay in the recovery of muscle strength differentiates ME from other forms of chronic fatigue syndrome (CFS).

The second component of what has been called ‘the diagnostic triad” for ME is cerebral dysfunction. Impairment of memory and concentration is extremely common, and hyperacusis may alternate with periods of normal hearing or even deafness. Emotional fragility is also a feature, and one third of patients experience significant problems with their balance. The third group of symptoms is related to circulatory impairment. Patients often complain of cold extremities and many will have an abnormally low temperature if examined at that time. Also characteristic is a grey facial pallor, which will be detected by relatives or friends about thirty minutes before the patient complains of feeling unwell.

It is important to note that the illness tends to fluctuate, not only from day to day, but from hour to hour (Dowsett et al, 1990; Dowsett & Welsby, 1992). Examination of patients conducted on ‘good days’ may give a misleading impression of both the illness, and the person suffering from it.

In terms of outcome, some patients appear to recover completely, some experience alternate remissions and relapses, some remain relatively stable while a quarter follow a deteriorating course and become severely disabled (Editorial, 1978; Goudsmit, 1996; Ramsay, 1988).

Measures such as the physical functioning subscale of the Medical Outcomes Study have shown significant impairment comparable to that reported by people with congestive heart failure and multiple sclerosis (Goudsmit, 1996). The illness is also associated with considerable emotional distress, which may manifest itself in a clinical disorder and is likely to undermine effective coping and adjustment (Yeomans & Conway, 1991).

The aetiology of ME is unclear but some cases are associated with enteroviral infection (Innes, 1970, Lane et al, 2003; McGarry et al, 1994), and there is evidence of abnormalities both in muscle (Behan et al, 1991; Lane et al, 2003) and in the brain (Costa et al, 1995). However, research into classic ME has been limited since the introduction of the concept of CFS which diverted attention to a larger population, and placed more emphasis on fatigue and pain (Fukuda, 1997; Jason et al, 2005; Kennedy et al, 2004; Wessely et al, 1997). Since the development of the initial research criteria for CFS, it has become clear that there are notable differences between subgroups or patients stratified according to presence or absence of a specific variable (Jason et al, 2005). As a result, the International Study Group advising the Centers of Disease Control and Prevention recommended that more research be focused on subtypes (Fukuda et al, 1994, Fukuda, 1997) and this has led to a recent resurgence of interest in infection-related fatigue and conditions resembling ME (Cameron et al, 2006; Jason et al, 2003; Kerr and Tyrrell, 2003; Vernon et al, 2006).

For instance, one study found that patients with ME reported more cognitive and somatic symptoms such as poor memory and concentration, dizziness, increased sensitivity to light and temperature disturbances, than people meeting the current criteria for CFS (Jason et al, 2003). This is significant since most of the rehabilitation programmes currently recommended for people with CFS do not address the range and complexity of symptoms documented in ME, and tend to explain the perpetuation of the illness primarily in terms of prolonged inactivity and stress (Burgess, 2006). However, very few people with ME have signs of disuse such as muscle wastage, and the cognitive impairments which have been documented tend to be specific and not reflective of a general ‘dulling down’ (Smith, 1991). Also of interest is the finding by Paul et al, (1999) of reduced muscle strength and the delay in the recovery of muscle power. These abnormalities appear to be absent or much more limited in patients with CFS (Lloyd et al, 1988).

In practice, it is difficult to study ME. Firstly, it is much less common than CFS as currently defined - 1 per 1000 versus 26 per 1000 in the UK, respectively (Ho-Yen & McNamara, 1991; Wessely et al, 1997), and consequently, there are fewer patients with well-defined ME available for research. Secondly, there is as yet little awareness in the UK of the differences within the population diagnosed with CFS and many within the scientific community may therefore not realise the value of encouraging and funding research into subsets.

This current study was possible because two of the authors lived near a number of senior physicians who were familiar with the illness as described in the older literature and who continued to make the diagnosis where appropriate. We were therefore in the fortunate position of having access to a small but well-defined group of patients with ME (Ramsay, 1988).

The aim of the current study was firstly, to determine the magnitude of illness intrusiveness in patients with well-defined ME and secondly, to assess the relationship between symptoms, co-morbid disorders, physical functioning and illness intrusiveness.

 

Method

Participants and procedure

The participants were recruited from a local patient support group in South London through a notice in their newsletter. In addition, one of the authors contacted a number of patients directly, through her work as a psychologist and researcher into ME. None were paid for their participation.

All the patients had been diagnosed by a physician and met the clinical criteria for ME as described in Dowsett & Welsby (1992). Patients also had to record a score of at least 2 on the items in the Profile of Fatigue–Related Symptoms (PFRS) which assess the presence of muscle weakness after exercise. Co-morbid conditions were not excluded if they were relatively minor and clearly separable from the ME. Of the 24 patients, 8 had additional disorders, which included asthma, migraine, back and neck pain, and a frozen shoulder.

 

Measures

The Illness Intrusiveness Rating Scale (IIRS)

Illness intrusiveness was assessed using the 13-item Illness Intrusiveness Ratings Scale (Devins et al., 1983, Devins et al, 2001). Participants were asked to rate the extent to which their illness ‘interferes’ with each of 13 life domains along a seven-point scale (1 ‘not very much’ or ‘not applicable’ to 7 ‘very much’). The life domains include health, diet, work, active recreation (e.g. sports), passive recreation (e.g. reading), financial situation, relationship with partner, family relations, social relations, religious expression and community and civic involvement. The scores were summed to allow comparison with other populations. The IIRS has been shown in previous research to have good construct validity and high internal consistency (e.g. Devins et al, 2001; Schimmer et al, 2001) and in this study, Cronbach’s alpha was .71 (n=23).

The Profile of Fatigue-Related Symptoms (PFRS)

This 54-item measure developed by Ray et al, (1992) assesses the pattern and severity of a number of symptoms commonly reported by patients with ME and post-viral fatigue syndrome. Respondents rate the extent to which they experienced symptoms during the past week on a 7-point scale from 0 ('not at all') to 6 ('extremely'). The score is the mean of the items for each subscale.

A principal components analysis of the original data yielded 4 scales: emotional distress, cognitive difficulty, fatigue and somatic symptoms. The internal consistency of each of the scales was high, ranging from .88 to .96, while the correlations between the scales were lower (range .44-.64). The test-retest reliability was high (range .86-.97) and the subscales correlated well with the relevant mood and symptom measures. In this study, we will not report the scores for emotional distress as the HADS permits a more meaningful comparison with other samples.

Hospital Anxiety and Depression Scale (HADS)

This is a 14-item self-rating scale specifically designed to assess anxiety and depression in people with medical conditions (Zigmond & Snaith, 1983). It has two subscales: anxiety and depression, each with 7 items rated from 0 to 3. To reduce false positive ratings due to presence of symptoms common to medical conditions and affective disorders, items relating to somatic symptoms have been excluded.

The HADS is a reliable measure with a Cronbach's alpha of .93 for the anxiety scale and .90 for the depression scale (Moorey et al, 1991). It is widely used and has been compared with both clinical rating scales and standardised interviews (Snaith & Zigmond, 1994).

The total subscale scores range from 0 to 21. Scores from 0-7 indicate normal levels of anxiety and depression, scores of 8 to10 are regarded as indicating possible (borderline) cases of clinical disorder, while scores of 11 or above are considered to reflect probable cases of morbidity (Snaith & Zigmond, 1994).

The Medical Outcomes Study (MOS): physical functioning subscale

Originally adapted from the Rand Health Insurance Experiment, the MOS Short-Form consists of 20 items focusing on physical and role functioning, mental health, health perception and pain (Stewart et al, 1988). The subscale evaluating physical functioning contains 6 items which assess the extent to which health interferes with a variety of activities, e.g. walking, sport, climbing stairs etc. The values range from 0 to 100 with higher scores reflecting better health. This measure is both short and reliable (α = .86), and has been used to assess a number of patient groups, including people with hypertension, coronary heart disease, diabetes, myocardial infarction and depression.

Functional Impairment Scale

This measure consists of four visual analogue scales covering the ability to work, manage the home, and take part in social and private leisure activities (Marks, 1986). Participants are asked how much their condition has affected each of the designated areas, with ratings ranging from 0 ('not at all') to 8 ('very severe'). The scores are summed and treated as a single variable. This measure of functional impairment has been used in previous research on ME (Goudsmit, 1996).

 

Statistical analysis

The ordinal data were analysed using independent sample T-tests or the Mann-Whitney test where appropriate and the categorical data were assessed using Fisher’s Exact test. The relationships between illness intrusiveness and the other variables were examined by computing Pearson correlation coefficients. The only exception was duration of illness, where the distribution of the scores was positively skewed and Spearman’s Rho was used instead. Since the illness intrusiveness score from one of the participants was extremely low, it was treated as an outlier and omitted from all calculations. Alpha was set at .05 and all tests were two-tailed.

 

Results

All the individuals who agreed to participate in this study completed and returned their questionnaires. There was no difference on any variable between the patients recruited from the support group and those who were approached directly by the psychologist. The mean age of the sample was 44.7 years (SD 7.03) and the average duration of illness was 103.6 months (SD 76.02). Eighteen (75%) of the participants were female and the same number had completed at least one year of further education. Sixteen (66.7%) were unemployed, on sick leave or retired at the time of the study and 20 (83.3%) reported that they had to leave or change their job due to the illness. Many of the participants were taking antidepressants and/or nutritional supplements at the time of the study or reported that they had taken them in the past.

The demographic and illness-related characteristics for two subgroups, with and without co-morbid disorders, are presented in Table 1 (see end of paper). The people with additional disorders, the ME-plus group, were slightly older and had been ill longer. Conversely, the ME group included a greater proportion of women (81% versus 62.5%) and more people who were married or co-habiting (62.5% versus 37.5%).

The results on the illness-related measures are presented in Table 2. Both groups were severely affected by the illness as shown by the scores for illness intrusiveness and physical functioning. The illness had a marked impact on all life domains, notably on active recreations such as sports, (mean = 6.70, SD = 0.64), and activities relating to work (mean = 6.65, SD = 0.71). ME had less effect on religious expression (mean = 2.26, SD= 1.76).

Both groups also reported severe fatigue, which is consistent with the extremely low scores for physical functioning and second measure of functional impairment. The mean scores for depression and anxiety were within normal limits but 19% of the ME group and 43% of the ME plus group recorded scores above the cut-off point for probable clinical depression. Similarly, 25% of the ME group and 29% of the ME plus group had scores above the cut-off point for probable clinical anxiety.

No significant differences were found between the groups on any of the variables, consequently the relationships between illness intrusiveness and the other illness and disability measures were assessed using the data for the two groups combined.

The results of the Pearson’s correlation coefficients are shown in Table 3. There was a strongly significant correlation between illness intrusiveness and cognitive dysfunction (r = .63, p = .001) and a more modest relationship between illness intrusiveness and fatigue (r = .47, p = .023). Of the mood indicators, illness intrusiveness correlated significantly with depression (r = .58, p = .005) but not with anxiety (r = .29, p = .19). As expected, there was a highly significant negative correlation with physical functioning (r = -.50, p = .016) indicating that those with greater impairments perceived the illness as more intrusive. There was also a significant association with the second measure of functional impairment (r = .68, p<.001). The correlations between illness intrusiveness and somatic symptoms, duration, education and age all failed to reach significance.

To explore if the relationship between illness intrusiveness and physical functioning was affected by emotional distress, acknowledged as a significant problem in this population and therefore a possible source of confounding, the correlation coefficient between the two variables was computed while controlling for depression. The correlation was lower (partial r = -.36, p = .10), indicating that at least part of the relationship was influenced by depressive mood. The same analysis was repeated for cognitive dysfunction and fatigue, and although there was a slightly lower correlation between illness intrusiveness and fatigue (partial r = .42, p = .06), the correlation with cognitive difficulty remained significant (partial r = .62, p = .003). Thus the effect of cognitive dysfunction in this patient group is probably not affected by the presence of depression.

Similarly, the relationship between illness intrusiveness and both fatigue and cognitive symptoms were examined while controlling for level of disability, as indicated by physical functioning. This analysis was also included in many of the studies by Devins and his colleagues to clarify the inter-relationships between variables. Both the correlation coefficients were lower, particularly the association with fatigue (partial r = .20, p = .38). However, the correlation with cognitive dysfunction remained significant (partial r = .51, p = .015).

 

Discussion

This study found that people with ME had extremely high scores on the illness intrusiveness rating scale. The total values for both groups were higher than those documented for patients with cancer, multiple sclerosis, rheumatoid arthritis and psychiatric conditions such as obsessive-compulsive disorders and bipolar disorder (see Table 4). The effect of co-morbid disorders further increased the perceived intrusiveness, as it does in relation to other conditions (Devins et al, 1993c; Masellis et al, 2003; Mucsi et al, 2004).

The disabling nature of ME, with and without additional disorders, was also reflected in the scores for physical functioning and functional impairment. The physical functioning score of 34.38 for the ME group is lower than that found in people with strictly-defined CFS (54.5), and persons with congestive heart failure (47.5), multiple sclerosis (53.2), depression (71.6) and diabetes (67.7) (Komaroff et al, 1996). However, in relation to functional impairment, the results from the present study were similar to those reported in people with ME recruited from a specialist clinic and patients with post-infectious fatigue syndrome attending a local hospital (Goudsmit, 1996).

As expected, the greatest impact of the illness was on physical activities. In this context it is important to consider not only the fatigue associated with ME, but also the muscle weakness following minimal exertion. The lack of muscle strength and the failure to recover during the 24 hours after exertion ends was documented objectively by Paul et al, (1999). Although this aspect of the illness is consistent with the reports of post-exertional fatigue, the latter is not a requirement for the diagnosis of CFS, and is not reported by all those who fulfil the criteria for this condition (Komaroff et al, 1996b).

The extent of the disability is further reflected in the scores for fatigue and cognitive difficulty. In the present study, the scores for both symptoms were slightly higher than those reported by Ray et al, (1992) who assessed patients with post-infectious fatigue (4.12 versus 3.75 for fatigue; 3.25 versus 2.74 for cognitive difficulty). However, they were similar to the scores found in people attending a specialist ME clinic and patients with post-viral fatigue (Goudsmit, 1996).

The mean score for somatic symptoms, including muscle weakness following trivial exertion, was also similar to those reported in previous studies, and correlated significantly with both fatigue and cognitive difficulty. However, like the other symptoms, there was only a weak association with depression.

One unexpected finding was that somatic symptoms did not correlate with illness intrusiveness. This may be due to the limited number of complaints included in the PFRS, the less disabling nature of the symptoms, or the use of effective coping strategies to reduce their impact. In contrast, cognitive difficulty showed a much stronger relationship with illness intrusiveness, suggesting that impaired cognition may interfere with information processing, and hence decision making and adaptation. The association with illness intrusiveness appeared to be independent of depression but was moderated, to a degree, by the level of disability as measured by physical functioning. The size of the sample did not permit a more comprehensive analysis of the relationship between the variables but the strong association between cognitive difficulty and perceived intrusiveness shows that this symptom may be a significant source of disability. The findings also indicate the need for more research to identify effective ways of limiting the effects of cognitive impairment and for the recognition of this aspect of the illness in rehabilitation programmes. The more modest correlation between fatigue and illness intrusiveness is consistent with previous studies on patients with ME and post-infectious fatigue (Goudsmit, 1996).

With regard to the theoretical framework proposed by Devins et al, (2006), the results provide some support for the hypothesis linking illness intrusiveness with disease-related factors and depression. Thus there was a significant correlation between perceived intrusiveness and depressive symptoms, a finding also documented in people with multiple sclerosis, end-stage renal disease (Devins et al, 1993d) and rheumatoid arthritis (Devins et al, 1992). However, the correlation between physical functioning and illness intrusiveness was influenced, in part, by the level of depression.

Contextual variables such as age and duration, identified by Devins and his colleagues as potential influences on the perception of disease, were not related to illness intrusiveness in this patient group (cf. Devins et al, 2006, 1992). The role of gender could not be evaluated, as there was an excess of female patients, as is common in research on fatigue.

While the study revealed modest correlations between fatigue and cognitive difficulty on the one hand, and illness intrusiveness, on the other, none of the symptom subscales were associated with anxiety or depression. Previous studies have also failed to find significant correlations between symptoms and psychological variables although this may have reflected the choice of instruments or differences between conditions (Bloom et al, 1998; Devins et al, 1992). For instance, Devins et al, (1990b) reported a relationship between muscle cramps associated with end-stage renal disease and pessimism, but not with depression and distress. In the studies on fatigue syndromes, Goudsmit, (1996) found that both fatigue and somatic symptoms correlated with anxiety in people with ME while all three symptom subscales correlated with anxiety and depression in patients with post-infectious fatigue. In contrast to the present study, both these samples were recruited from specialist NHS clinics and most had been ill for a shorter time.

Although there was no significant association between symptoms and depression, the scores on the HADS showed that many patients experienced considerable emotional distress. Indeed, one in five of the ME group and over 40% of the ME plus group had scores above the cut-off point for probable clinical depression and about a quarter in both groups had scores suggesting clinical anxiety. The increased prevalence of marked anxiety and depression has also been observed in other studies on ME and CFS (Goudsmit, 1996, Yeomans & Conway, 2001). As most of the patients had been ill a long time, it is possible that many had developed effective coping strategies to cope with their symptoms. However, the correlation between illness intrusiveness and depression suggests that aspects of the condition other than symptoms and level of disability, may have contributed to, or exacerbated emotional distress.

One factor which may play a role in this respect is the uncertainty related to the illness. In previous research, Goudsmit, (1996) found that uncertainty was a predictor of both anxiety and depression in patients with ME. It was hypothesized that this reflected not only the lack of knowledge about aetiology and prognosis, but also the paucity of treatments, particularly, for the more severely-affected. She also identified issues in relation to social support and the fear of rejection, as a result of the media portrayal of the illness and the continuing doubts about the legitimacy of the condition. Although there has been some coverage of the biomedical research, many articles have tended to emphasize psychological issues such as the role of cognitive-behavioural factors, and the view that ME is an excuse to escape the rat race or a means to avoid the stigma of mental illness (Barsky & Borus, 1999; Henningsen & Priebe, 1999; Silver, 1994). Like patients with a stigmatising illness, some people with ME may choose to limit their exposure to negative comments by avoiding certain activities, thus reducing their access to positive outcomes and increasing the intrusiveness of ME (Taylor et al, 2005).

On a practical level, therapists can offer emotional support and teach patients ways to reduce the uncertainty caused by the marked fluctuation of symptoms. One strategy, colloquially referred to as ‘pacing’, has been discussed in patient literature since 1989 (Goudsmit, 2005) and requires people to keep within the limits imposed by the illness. In surveys of support groups, respondents have consistently rated this approach as one of the most helpful coping strategies for ME and strictly-defined CFS1 , and it is also becoming more widely accepted by practitioners as a valid alternative to graded exercise (De Ridder et al, 2004; Jason et al, 2005; Nijs et al 2006; Saidi & Haines, 2006). Adding pacing to a self-management or rehabilitation programme helps to limit the exacerbations caused by overexertion and gives patients a greater sense of control. The illness therefore becomes more predictable and less disruptive, which may help to reduce physical impairment and increase subjective well-being (Goudsmit, 1996).

Another aspect of the illness which therapists can address is the complexity of ME. Much of the media interest in recent years has been directed at CFS, with the emphasis on fatigue and pain. The theory of deconditioning, often cited in relation to CFS, cannot explain the diversity of symptoms or the marked diurnal fluctuations associated with ME (Dowsett & Welsby, 1992; Editorial, 1987), and many patients have become disillusioned with the narrow perspective offered by orthodox science, leaving them vulnerable to exploitation by seemingly understanding but less qualified practitioners.

At the moment, most patients with ME are managed in the same way as people with CFS. However, it is not clear if interventions such as cognitive-behaviour therapy (CBT) are as effective for ME as they are for patients with chronic fatigue. Alternative approaches focused on treating individual symptoms, and offering advice on diet and pacing as well as counselling where required, have been found to be helpful for people with post-infectious fatigue (Goudsmit, 1996). Likewise, patients with ME may also benefit from self-management training programmes devised to help people cope with a chronic disease (Barlow et al, 2005). These and the new, individualized programmes for CFS (Thomas et al, 2006) address a greater range of symptoms and offer additional therapeutic options which may lead to a significant reduction in the perceived intrusiveness of, and emotional distress associated with ME.

To summarise, this study has shown that cognitive impairment plays an important role in ME, and that this aspect of the illness deserves greater recognition. The severity of the symptoms and the extent of the disability means that generalisations from other fatigue syndromes to ME should be interpreted with caution. Further research into the factors which influence illness intrusiveness may help health professionals to offer more appropriate and effective interventions.

 

Caveats

This exploratory study has a number of limitations. The small size of the sample and the fact that the participants were partly self-selected means that the results should not be generalized to other ME populations. Moreover, the patients had been unwell for a comparatively long time and the findings may therefore not be applicable to those with a shorter illness. The research was also limited by the lack of measures to assess psycho-social well-being and other indicators of quality of life, and the nature of the design means that it is not possible to establish causal directionality among the variables tested. Finally, while we assessed fatigue, cognitive impairment and somatic symptoms, the measure used was rather limited and this may have given a misleading view of the range and severity of neurological and immunological complaints experienced by patients with ME.

 

Conclusion.

ME causes significant disruption to all aspects of a patient’s life. The high score on the illness intrusiveness rating scale underlines the need for more research into this condition, and the correlation between cognitive impairment and perceived intrusiveness indicates the importance of studying a wider range of symptoms. Further research is required to clarify the relationships between disease-related factors, illness intrusiveness and psychological outcome in ME as well as other fatigue syndromes.

 

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Footnote.

1. See for example, The CFIDS Chronicle, CFIDS Association. July/August 1999.

 

 

Table 1. Demographic and illness-related characteristics for the ME and ME plus groups.


Characteristic

ME

ME plus


Patient Characteristics

Mean Age (N, years) 16 43.75 8 46.63
Gender    
     Male 3 3
     Female 13 5
Marital status    
     Unmarried 6 5
     Married/cohabiting 10 3
     Widowed/divorced 4 0
Education beyond 16 (years) 5.88 5.62

Employment status

   
     Full-time 2 0
     Part-time 1 0
     Not working 10 6
     Other (housewife/student) 3 2
     Changed or lost job due to illness (N, %) 14 (93.3)a 6 (75%)

 

Illness characteristics

Duration (months, SD) 99.44 (56.98) 112.00 (109.14)
Range 30-264 18-348
Onset    
     Acute (N, %) 9 (56.3) 5 (62.5)
     Post viral 11 (68.8) 5 (62.5)
Under treatment (N, %) 12 (75) 7 (87.5)

a N=15.

 

 

Table 2. Illness intrusiveness, severity of symptoms and disability measures in the ME and ME plus groups


Measure

ME

ME plus

  Mean (SD) Mean (SD)
  (N=16) (N=8)

Illness Intrusiveness Rating Scale

63.27 (11.02)a

 72.00 (9.24)
Fatigue (PFRS) 4.12 (1.47) 3.69 (1.17)
Somatic symptoms (PFRS) 2.47 (1.08) 2.77 (1.50)
Cognitive difficulty (PFRS) 3.25 (1.19) 3.32 (1.54)
Anxiety (HADS) 7.56 (3.63) 9.00 (6.14)b
Depression (HADS) 6.19 (3.25) 8.71 (2.57)b
Functional impairment 24.13 (4.35) 24.25 (3.66)
Physical functioning (MOS-SF) 34.38 (23.35) 35.42 (18.77)

Abbreviations: PFRS Profile of Fatigue Related Symptoms, HADS Hospital Anxiety and Depression Scale, MOS-SF Medical Outcomes Study-Short Form.

a N=15
b N=7

 

 

Table 3. Correlation between illness intrusiveness, symptoms and disability.


 
Illness intrusiveness Fatigue Somatic symptoms Cognitive dysfunction Depression Physical functioning Functional impairment
Illness intrusiveness
 

.47*

.36

.63** .58** -.50* .68**
Fatigue
 

 

.55**

.56** .24 -.71** .65**
Somatic symptoms
 

 


 

.37 .16 -.50* .34
Cognitive dysfunction
 

 


 


 
.24 -.49* .60**
Physical functioning
 

 


 


 
    -.61**

Pearson’s correlation coefficients (two-tailed) using data from both groups combined (N=23).

* p<.05

** p<.01

 

 

Table 4. Means for illness intrusiveness in different chronic illness groups.


Diagnostic group

IIRS Total

Reference


Obsessive-compulsive disorder 57.4 Anthony et al. (1998)
Social phobia 54.6 Anthony et al. (1998)
Bipolar disorder 53.5 Robb et al. (1997)
Panic disorder 53.3 Anthony et al. (1998)
Systemic lupus erythematosis 44.7 Edworthy et al. (2003) a
Multiple sclerosis 43.5 Devins et al. (1993b)
Irritable bowel syndrome 40.5 Dancey et al. (2002)
Heart transplant 39.9 Schimmer et al. (2001)
Kidney transplant 38.9 Schimmer et al. (2001)
End-stage renal disease 38.8 Devins et al. (1993a)
Rheumatoid arthritis 37.9 Devins et al. (1993a)
Bone marrow transplant 37.5 Schimmer et al. (2001)
Six cancer groups 33.8 Devins et al. (2006) a
Laryngectomy 33.1 Devins et al. (1994) a
Liver transplant 32.2 Schimmer et al. (2001)
Cervical cancer 32.1 De Groot et al. (2005)
Osteoarthritis 26.1 Edworthy et al. (1999) a

All entries represent group means. Where there is more than one score for an illness, the table shows the highest. All data are for conditions without co-morbid disorders.

a Devins. Pers. comm.

 

 

Acknowledgements. We wish to thank all the patients who participated in this study, and Ms. Mary Sullivan and Ms. Elaine Sturman for their helpful comments on earlier drafts.