Fatigue in multiple sclerosis is related to disability, depression and quality of life
Introduction
Fatigue is a common and disabling symptom in multiple sclerosis (MS), but it was overlooked for a long time probably because the measurement of this subjective symptom was difficult. Patients perceive fatigue as an abnormal and excessive symptom different from their prior experience without disease [1], [2], [3].
Fatigue can be defined in a number of ways, as a lack of physical or mental energy or a feeling of tiredness [4].
Fatigue is reported by 50–90% of patients according to different studies (53% for Colosimo et al. [5]–92% for Fisk et al. [6]). It is sometimes the most disabling symptom (40% for Murray [2], 14% for Fisk et al. [6], 28% for Krupp et al. [3]) and the first sign of the disease [6], [7].
It can be responsible for an increase in other symptoms in 48% of reported cases [1].
Fatigue may be a major reason for unemployment among patients with multiple sclerosis [8].
It can affect social relations, daily activities, cognitive and physical domains [9]. Fatigue assessments in MS must take these aspects into account.
In recent years, many different fatigue scales have been used [6], [10], [11], [12], but unlike the EDSS, there is no one international standard, so it is difficult to compare levels of fatigue. As a result, there is neither consensus of opinion nor a common way to assess the different aspects of fatigue. Furthermore, a problem arises regarding original English fatigue scales when they are used in another language without checking the psychometric properties of the instruments. Simple word-for-word translations do not take cross cultural aspects into account, leaving these studies more open to criticism. Fisk et al. have elaborated the Fatigue Impact Scale (FIS), an accurate instrument, which identifies the effects of fatigue on MS subjects [6], [13].
As fatigue in MS is a multidimensional symptom, this instrument also includes three subscales identifying different and accurate features of fatigue. Items were drawn from clinical experience and from data collected during interviews of MS patients in which they reported the impact of fatigue in daily living. A study comparing different fatigue scales has suggested that FIS was the most relevant instrument assessing fatigue [14].
Previous studies on fatigue in MS have found significant correlations between higher fatigue and higher disability [5], [7], [15], [16], progressive rather than relapsing remitting disease [5], [7], higher depression [15], [17], [18], [19], [20], or quality of life impairment [21]. But the results appeared to be controversial by other authors who showed that fatigue appeared to be a symptom independent of disability [3], [6], [22], disease course [15], [19] and depression [3], [6], [22]. The interest to clarify these relations may help to improve the management of fatigue.
The aim of the study was to determine the relationship of fatigue with disability, disease course, depression and quality of life in a large sample of patients who were evaluated for clinically definite multiple sclerosis at the University Hospital in Nancy.
Section snippets
Patients
Three hundred and twelve outpatients from the University Hospital in Nancy, with clinically definite multiple sclerosis based on Poser et al.'s criteria [23], were selected for this study as part of the European database of EDMUS [24]. We selected MS subjects who were ambulatory and had Expanded Disability Status Scale (EDSS) scores [25] of ≤ 6.5.
Patients were excluded when they suffered from another chronic disease in which they could experience fatigue, such as rheumatic diseases, serious
Results
Two hundred and thirty-seven (76%) patients completed all three scales (EMIF-SEP, shortened form of Beck Depression Inventory and SF-36) entirely and were included in the study. Sixty patients who had not answered to at least one item were excluded as were fifteen patients who had not returned the questionnaires. The selected subjects (169 females and 68 males) had an average age of 42.5 ± 10.9 years (range 18–73 years), average disease duration of 9.8 ± 7.4 years (range 8.3 months to 36.7 years).
Discussion
This study shows significant correlations between greater fatigue in multiple sclerosis and higher disability, between greater fatigue and more severe depression, and between greater fatigue and quality of life impairment. To this end, we used a representative population of two hundred and thirty-seven patients with clinically definite multiple sclerosis as diagnosed via the criteria of Poser et al. [23]. However, the results are different between the four dimensions of fatigue and confirm the
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