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Ankylosing spondylitis (AS) is a rheumatic inflammatory disease mainly affecting the spinal and axial joints, and is often accompanied by restricted mobility in these joints (1). More than half of the patients with AS report that fatigue is a major problem (2–4), and fatigue is used as a measure of disease activity (5). It has been suggested that fatigue in rheumatic inflammatory diseases is related to inflammation, but no associations have been found between fatigue and inflammatory markers in patients with AS (6, 7). However, fatigue is associated with pain (2, 6) and impaired mental (4, 6) and physical functioning (2, 4, 8). In the present study, it is assumed that fatigue results from interactive processes between the individual with AS, their daily activities and social life, and their illness and disability. In AS, both the illness (9) and its impact on life situations (10) may vary. This raises the question of how fatigue varies for the individual. Cross-sectional studies have demonstrated that fatigue severity varies considerably within patient groups with AS (2–4, 6–8, 11).
Fatigue is a universal and common experience both in sickness and health (12, 13). Some authors have applied tiredness to illuminate fatigue experienced by healthy individuals and fatigue experienced by sick people (14). Tiredness is considered a natural response to life strain, such as strenuous activities, busy day schedules, and emotional stress. It is usually not present all the time and varies according to the time of day, whether it is a good or bad day, and the individual's general life situation. Common means of recovery are rest, relaxation, sleep, and engagement in a positive activity. Fatigue can be the first symptom of a disease and an important element in disease symptoms in several chronic diseases (13). In accordance with these interpretations, tiredness has been defined as “a universal sensation that is expected to occur normally at certain times of the day or after certain types of activity or exertion,” and fatigue as “an uncommon, abnormal or extreme whole bodily tiredness which is not related to activity or exertion” (15). These definitions underline that fatigue differs from what is normal tiredness by occurring unrelated to activity and being more severe. These understandings became important in the process of interpreting the present data. Often fatigue is referred to as “disease-related fatigue,” but presently I have applied the concept “illness related,” since disease connotes a medical explanation, whereas illness refers to a patient's explanation (16), which is in focus in this study.
The aim of the present study was to examine the nature of fatigue and how it is managed in daily life situations by individuals with AS.
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Currently, 2 different conditions of fatigue have been identified: a comprehensible, manageable, life strain–related tiredness, and an unfamiliar, unmanageable, illness-related fatigue.
Life strain–related tiredness was mainly considered by the respondents to be comprehensible and therefore natural in the sense that the tiring situations and recovery strategies were familiar to them and similar to their prior experiences as healthy individuals. They also thought that healthy people around them reacted in the same way. In other words, life strain–related tiredness and recovery were linked to their daily life situation. However, they did admit to being more easily tired, needing to rest more frequently, and not sleeping as well as before their illness. On the other hand, they considered it reasonable to need more frequent rest during the daytime when they had slept badly the night before, and to become tired more easily when they had to work harder to manage body stiffness. They found that resting and reducing their life load were important self-management strategies for coping with tiredness. It has been found that patients with cancer undergoing strenuous radiation and chemotherapy also consider fatigue to be natural (22). However, these authors also reported that when fatigue persisted after completion of therapy, their respondents no longer considered it natural because it had become incomprehensible (22). Therefore, fatigue seems to be found natural by individuals when it can be explained by specific situations. The condition of life strain–related tiredness fits in with the findings from qualitative studies on tiredness in healthy individuals, who have described their tiredness as a temporary and comprehensible reaction and who have reported that they obtained relief by sleeping, resting, and slowing down (14, 23). This is also in line with the definition of tiredness as “a universal sensation that is expected to occur normally at certain times of the day or after certain types of activity or exertion” (15).
The respondents experienced illness-related fatigue as being unlike their previous experience as a healthy individual. It occurred unexpectedly, had no understandable reason, and could not be relieved by the usual self-management strategies. This is in line with the definitions of disease-related fatigue (15). The respondents thought it was related to inflammation. This seems plausible, but requires a study of the biologic factors during a period of illness-related fatigue.
The traits of unmanageability, strangeness, or uncommonness characterizing illness-related fatigue in this study correspond to reports from individuals experiencing fibromyalgia (14), cancer (23–25), human immunodeficiency virus (26), multiple sclerosis (27, 28), and rheumatoid arthritis (RA) (29–31). One obvious difference in the reports on fatigue in these patient categories and AS is that in AS there seem to be periods with life strain–related tiredness that sometimes changes to illness-related fatigue. Such a distinction is not described in the other patient samples. The studies of patients with RA (29–31), however, suggest that both tiredness and fatigue may be present at the same time because fatigue has been described both to be predictable and unpredictable, to be dull and overwhelming, to precede and not to precede a particular activity, and to be manageable and unmanageable. Therefore, it might be that life strain–related tiredness and illness-related fatigue are more intertwined in patients with RA than among those with AS.
In a systematic meta-study of qualitative studies of fatigue, the authors raised the questions of whether the dynamic nature of fatigue had been captured in the 35 studies they reviewed, and why fatigue was attributed solely to disease and regarded as a distinct entity in chronic diseases (32). The authors speculated that in investigations into the meaning of fatigue, the dynamics of fatigue may have been lost because it is associated with interactive processes between a person and social life. The present findings suggest that this hypothesis is a fruitful one. Examining interactions between the individual and their everyday activities during different periods of illness enabled me to see the clear differences between the descriptions of fatigue conditions and which were associated with life strain and which had no apparent association to what the respondent did in everyday life. Moreover, when rereading the interviews, I found that the respondents used a variety of terms to describe fatigue, but that these usually applied to both tiredness and fatigue. Thus, it was not the words they used, but the context of their statements and the descriptions of what they did to recover that enabled me to identify the differences between the tiredness and fatigue conditions. Therefore, future studies examining fatigue in other social contexts and situations are needed.
The trustworthiness of a study depends on whether it has been performed in a way that enhances the credibility of the findings (33). Obtaining rich data about fatigue was difficult in the beginning. But a qualitative design has the advantage in such cases of being flexible, so that I was able to formulate better questions in the course of the interviews, and I also had time between interviews to critically reflect about how my preconceptions may have shaped my questions and interpretations during the interviews. Initially, my clinical experience from previous patient encounters and my own experience of tiredness hampered my ability to obtain in-depth information. Their stories seemed too familiar to me. However, after I started to ask about fatiguing everyday situations, I was able to ask for more in-depth information and capture more nuanced data. Another important methodologic issue is that of transparency (33). My discussions of results with colleagues forced me to explain the various steps of the study clearly. A limitation of the analysis of fatigue, however, is that the interpretations were not validated by other researchers, the respondents, or other individuals with AS.
The qualitative interview is intended to obtain individual, contextual, and situational data, whereas the analysis is intended to develop knowledge that can be transferred to other individuals and applied in other contexts and situations. The transferability of my previous descriptions of different illness conditions (10) developed from the same data material seems to be good because the findings have attracted great interest among individuals with AS and have been published in the AS patient organizations' German, Danish, Norwegian, and international journals. This does not necessarily mean that the present findings are transferable, however. But transferability is also enhanced by data variability. In the present study, a heterogeneous clinical sample of individuals was interviewed, and they provided rich information. The respondents were ages 30–59 years and were mainly recruited among individuals in therapy. This means that the findings are not necessarily transferable to younger or older individuals with AS or to nonclinical groups.
The clinical implications of my findings might be that clinicians can be inspired to question and interpret the experience of fatigue in a more nuanced way in their clinical examination. The 2 different categories of fatigue may also call for different therapeutic approaches. Life strain–related tiredness has a positive aspect in that it can protect against overstrain and can be relieved by self-management strategies and regulated by modifying everyday life strain. Moreover, it is likely that more life strain can be endured if physical fitness is improved. In contrast, illness-related fatigue does not seem to serve any purpose in guiding everyday life regulation. The present findings suggest that illness-related fatigue needs a medical therapeutic approach aimed at modifying disease processes.
By examining fatigue in terms of interactions between an individual, their illness, and the nature and context of their everyday experience, I have identified 2 different conditions of fatigue in individuals with AS. The condition of life strain–related tiredness is comprehensible and manageable, and is a sign to help patients to protect themselves from overstrain. The condition of illness-related fatigue is unfamiliar, unmanageable, and accompanied by severe bodily pain and stiffness. To my knowledge, no comparable studies have been performed on fatigue in AS, and future studies are needed in order to further illuminate this issue.