Support Care Cancer (2008) 16:241–249 DOI 10.1007/s00520-007-0298-8
ORIGINAL ARTICLE
Possible links between behavioral and physiological indices of tiredness, fatigue, and exhaustion in advanced cancer Karin Olson & A. Robert Turner & Kerry S. Courneya & Catherine Field & Godfrey Man & Marilyn Cree & John Hanson
Received: 16 February 2007 / Accepted: 12 June 2007 / Published online: 24 July 2007 # Springer-Verlag 2007
Abstract Goals In this theoretical paper, we present the Edmonton Fatigue Framework (EFF), a new framework for the study of tiredness, fatigue, and exhaustion in advanced cancer. K. Olson (*) : M. Cree Faculty of Nursing, University of Alberta, Edmonton, Alberta, Canada e-mail:
[email protected] A. R. Turner Department of Oncology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada K. S. Courneya Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada C. Field Faculty of Agriculture, Food, and Nutritional Science, University of Alberta, Edmonton, Canada G. Man Department of Pulmonary Medicine, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada J. Hanson Population Health and Information, Cross Cancer Institute, Edmonton, Alberta, Canada K. Olson Faculty of Nursing, University Extension Centre, 6-10 8303 112 St., Edmonton, Alberta T6G 2T4, Canada
Materials and methods The Fatigue Adaptation Model (FAM), the starting point for the EFF, was drawn from a literature review pertaining to fatigue in depression, chronic fatigue syndrome, cancer, shift workers, and athletes published in the Cumulative Index to Nursing and Allied Health Literature (CINAHL), Medical Literature Analysis and Retrieval System Online (MEDLINE), PubMed, PsychINFO, SPORTdiscus, and CancerLit between 1995 and 2004, and from seven qualitative studies conducted by our group. The EFF, an elaboration of the FAM, was constructed after an expansion of our literature review to 2006 and team discussion. The EFF provides new insights into possible links between behavioral and physiological indices of tiredness, fatigue, and exhaustion as they occur in both ill and non-ill states. In this paper, however, we consider only possible links in advanced cancer. Conclusions We propose that stressors associated with advanced cancer and its supportive treatment trigger declines in four systems—cognitive function, sleep quality, nutrition, and muscle endurance—and that these declines reduce one’s ability to adapt. While these systems each likely has its own effect on adaptation, we propose that the most important and serious effects arise from interactions among declines in cognitive function, sleep quality, nutrition, and muscle endurance. Conclusions Interventions for fatigue have been limited by a lack of understanding about its etiology. Hypotheses arising from the EFF` suggest a new direction for further study that focuses on interactions among cognitive function, sleep quality, nutrition, and muscle endurance. Keywords Fatigue . Cancer . Adaptation . Conceptual framework
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Introduction Symptom management is the cornerstone of advanced cancer care. Given the limited prognosis in advanced cancer, the clinical focus shifts to symptoms, such as fatigue, that interfere with quality of life [14, 46, 72]. The development of interventions for fatigue has been hampered by the lack of understanding about its etiology. Early research on fatigue explored the relationship between low hemoglobin levels and fatigue. It was hoped the increased hemoglobin levels that followed the administration of erythropoietin might also result in reduced fatigue, but this has not been the case. In a recent systematic review originally prepared for the Cochrane Library, Bohlius and colleagues showed that while the administration of erythropoietin is clearly associated with significant increases in hemoglobin, the evidence that it also reduces fatigue is inconclusive [10]. This is in keeping with our clinical observations that the correction of the anemia with administration of erythropoietin according to evidence practice guidelines [70] or of Packed Red Cells rarely ameliorates fatigue to the degree intended. This finding suggests that other stressors experienced by individuals with advanced cancer also contribute to fatigue.
Purpose and significance The purpose of this paper is to present a new conceptual framework, the Edmonton Fatigue Framework (EFF), for the study of fatigue. This framework is built on our Fatigue Adaptation Model (FAM), a new approach for the examination of possible links between behavioral and physiological indices of tiredness, fatigue, and exhaustion as they occur in both ill and non-ill states. In this paper, however, we focus on advanced cancer. For the purposes of this paper, individuals with advanced cancer are those for whom the objective of care has shifted from cure to supportive care in either the active treatment or the palliative setting. Our central thesis is that stressors related to disease processes in advanced cancer and to its treatment trigger declines in four key systems—cognition, sleep quality, nutrition, and muscle endurance—and that these declines inhibit the ability to adapt to stressors. The inability to adapt is marked by the onset of fatigue and a decline in quality of life. Behavioral indices are generally considered to be subjective in nature and, in some cases, to be observable by others. Most research on fatigue has relied only on behavioral indices. The problem with this approach is that as it relies primarily on perceptions of fatigue, any benefits attributable to preclinical detection are lost. Our interest is in finding physiological processes that correlate with
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behavioral indicators of tiredness, fatigue, and exhaustion. If we could identify these correlates, we may be able to identify early physiological changes that make it possible to detect impending fatigue before it is perceived. These early changes could provide targets for interventions that could prevent fatigue or at least delay its onset.
Development of the fatigue adaptation model In an earlier study, we unexpectedly found that certain behavioral patterns distinguished advanced cancer patients who reported fatigue from those who did not report fatigue [52]. Participants without fatigue reported some loss in energy but were able to estimate remaining energy and create new daily routines that incorporated both the demands of their compromised health status and treatments as well as activities that were meaningful to them. These components—the ability to assess remaining energy and to create new daily routines—formed the foundation of our original conceptualization of tiredness. The ability to create new routines was significant in our view because it indicated the ability to respond to stressors—in other words, “to adapt.” The ability to think clearly was critical to the ability to create new routines. Those who experienced fatigue, on the other hand, demonstrated behavioral patterns that appeared to interfere with adaptation. These patterns were characterized by either the inability to create a new daily routine or the development a routine that required more energy than was available. Thus, this study provided the initial behavioral markers that distinguished between fatigue and tiredness. In a second study, some participants with advanced cancer described attempting to develop routines that incorporated the demands of advancing disease but noted that regardless of the support provided, they were simply becoming “too tired” to continue living [53]. They described fatigue in terms of physical weakness, feeling tired but not sleepy, and lacking in energy. This study provided additional definition to our description of fatigue and suggested a state beyond fatigue where adaptation was not possible. To explore the distinctions between tiredness, fatigue, and exhaustion, a reconceptualization of fatigue was undertaken [47]. Consistent with the pragmatic utility approach to concept clarification, the research literature indexed between 1996 and 2004 in the Cumulative Index to Nursing and Allied Health Literature (CINAHL), Medical Literature Analysis and Retrieval System Online (MEDLINE), PubMed, PsychINFO, SPORTdiscus, and CancerLit was searched for material pertaining to fatigue in adult populations known to experience fatigue for different reasons (illness, work, or leisure activities). The populations
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used in this analysis were selected on the basis of the availability of sufficient literature to undertake a complete evaluation. The ill populations selected were cancer, major depressive disorder, and chronic fatigue syndrome, while shift workers were used to study fatigue in the context of work, and athletes were used to study fatigue in the context of leisure activities. Comparing literature from populations that experience fatigue for different reasons allowed us to strip away the context in which the fatigue occurred, making it easier to identify common attributes. Tables outlining the primary attributes of fatigue in each population were prepared by the research team. The attributes common across all five populations were: decreased stamina (speed, coordination, and strength) out of proportion to energy expenditure, decreased cognition, decreased sleep quality, increased emotional reactivity, decreased control over body processes, and decreased social interaction [50]. Embedded within these six attributes, however, were three subtle but distinguishable recurring behavioral patterns, suggesting the existence of three related concepts that existed along an underlying continuum (Fig. 1). We labeled these patterns Tiredness, Fatigue, and Exhaustion and labeled the continuum Adaptation because the changes in the behavioral patterns from tiredness to fatigue and from fatigue to exhaustion seemed consistent with decreased adaptation as outlined in the General Adaptation Syndrome (GAS) by Selye [64–66]. A detailed comparison of the FAM to other fatigue models is provided elsewhere [51], but it is most closely allied with the work of Glaus [29], Cameron [16], Rhoten [57], and Aistars [1], who viewed fatigue as a stress response rather than as a marker for alertness, as outlined in the more commonly used fatigue models built on the work of Grandjean [30]. To refine the FAM, we undertook qualitative studies in each of the study populations using ethnoscientific and grounded theory methods [49]. As the athletic literature is so large, our study of athletes included only those who were recreational distance runners. The cancer population included individuals with metastatic disease who were receiving supportive care in either active treatment or palliative settings. Data were collected using tape-recorded unstructured interviews. The interviews were coded by two members of the research team, and codes were examined to determine whether they matched the attributes of tiredness, Fig. 1 The fatigue adaptation model
fatigue, and exhaustion identified in the literature, and whether any new attributes not reported in the literature could be identified. Data were queried with respect to distinct changes that were qualitative in nature rather than simply a matter of degree or intensity. Changes corresponding to all three behavioral patterns identified in the literature were found for four of the attributes — stamina, cognition, sleep quality, and emotional reactivity. The behavioral patterns for body process and social interaction originally attributed to Tiredness, based on the literature, occurred in conjunction with the behavioral patterns for Fatigue in our studies; there did not appear to be any changes in body processes or sleep quality during Tiredness in any of the study populations. Examples of the classification decisions with respect to each attribute are outlined below. With respect to changes in stamina, weakness in proportion to the amount of energy expended was classified as Tiredness, while weakness sooner than expected and out of proportion to the amount of energy expended was classified as Fatigue. Sudden and unpredictable weakness, often without any identifiable energy expenditure was classified as Exhaustion. Changes in cognition showed the similar qualitative shifts between Tiredness, Fatigue, and Exhaustion. Forgetfulness was classified as Tiredness, while difficulty concentrating was classified as Fatigue. Confusion that resembled delirium (“couldn’t find my way home from the grocery store where I had shopped for 20 years”) was classified as Exhaustion. With respect to sleep quality, sleepiness was classified as Tiredness, while “difficulty sleeping” was classified as Fatigue. Unpredictable periods of “trouble staying awake” interspersed with periods when one could not sleep were classified as Exhaustion. Regarding emotional reactivity, impatience was classified as Tiredness, while anxiousness (not “increased” impatience) was classified as Fatigue. “Emotional numbness” was classified as Exhaustion. With respect to body processes, participants reported sensory changes (sensitivity to light, noise, and touch, and the development of a metallic taste in one’s mouth), gastrointestinal changes (nausea, diarrhea), and the need to exert extra mental effort to resist changes within their
Adaptation Tiredness Fatigue Exhaustion No Adaptation
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bodies (“fight to keep my eyes open’). These changes occurred at the same time as the changes in the attributes stamina, cognition, sleep quality, and emotional reactivity that we had classified as Fatigue. Participants reported that an overwhelming need to “lie down,” numbness, and an inability to move occurred in conjunction with changes in stamina, cognition, sleep quality, and emotional reactivity that we had classified as Exhaustion. Exhausted individuals said their bodies felt unfamiliar to them and that they seemed to “crash” at times that were not predictable. One woman said, “once my left leg starts to drag, I have to sit down because if I don’t, I’ll fall over.” With respect to social interactions, participants reported that having to “push” or “force” themselves to interact or “keep going” occurred in conjunction with the changes in stamina, cognition, sleep quality, emotional reactivity and body process that had been classified as Fatigue. Some individuals reported being unable to tolerate the stimulation associated with social interactions, even with close family members and friends, and chose to not participate even as an observer in activities they had previously enjoyed; this sensation occurred in conjunction with the changes in stamina, cognition, sleep quality, emotional reactivity, and body process that had been classified as Exhaustion. One of the most important findings in this phase of our research was that changes in body process and social interactions were not detectable until the behavioral patterns associated with fatigue in the other four attributes were also present. This suggests that the behavioral patterns for Tiredness with respect to sleep quality, stamina, cognition, and emotional reactivity could serve as early warning signs for impending Fatigue. Similarly, the onset of the behavioral patterns for Fatigue with respect to sleep quality, stamina, cognition, emotional reactivity, body processes, and social interaction could serve as early warning signs for impending Exhaustion. These findings are consistent with the early work of Bartlett [5] who noted that sensations associated with fatigue arrive too late to be of preventive value. Based on the literature review that lead to the FAM and on our qualitative studies, we developed the following conceptual definitions of Tiredness, Fatigue, and Exhaustion: –
–
Tiredness is characterized by forgetfulness, impatience, gradual heaviness or weakness in muscles after work, sleepiness alleviated by rest, but no change in social interaction or decreased control over body processes. Tiredness is an adaptive response and occurs during the alarm phase of the GAS outlined by Selye [64–66]. Fatigue is characterized by difficulty concentrating, anxiety, a gradual decrease in stamina, difficulty sleeping, decreasing control over body processes some
–
of which could be maintained with extra mental effort, and the limitation of social interaction to only those activities of particular significance. Fatigue indicates declining ability to respond to stressors and occurs during the resistance phase of the GAS outlined by Selye [64–66]. Exhaustion is characterized by confusion that resembles delirium, emotional numbness, sudden loss of energy in the absence of any identifiable energy expenditure, difficulty staying awake and difficulty sleeping, unable to control body processes despite extra mental effort, and complete social withdrawal. Exhaustion indicates almost complete inability to respond to stressors and occurs during the exhaustion phase of the GAS as outlined by Selye [64–66].
The interview data from all five studies were reviewed by the research team to identify statements that were common across populations and that were examples of the way stamina, cognition, sleep quality, emotional reactivity, and body process changed as individuals progressed from tiredness to fatigue, and from fatigue to exhaustion. This process resulted in the first draft of the Rapid Fatigue Assessment Screening Tool (rFAST). The tool and the definitions were circulated to 17 international fatigue experts, who were asked to comment on the fit between the items in the tool and the conceptual definitions. The tool was revised based on the information received, and a study to examine its construct validity is nearly completed. Both the results of our work outlined above and studies reviewed more recently suggest that changes in muscle endurance (stamina), cognition, sleep quality, and nutrition are the primary determinants of Tiredness, Fatigue, and Exhaustion. In the next sections of this article, we outline key studies that have shaped the development of these ideas. Stress and cancer Hypotheses about etiological relationships between stress and cancer have been discussed for many years [39]. More recently, many investigators have identified the symptoms of cancer and the short- and long-term effects of its treatment as stressors. For example, in a study comparing fatigued and nonfatigued breast cancer survivors, Bower et al. [12] demonstrated a significantly blunted response in cortisol, a common stress marker, in the fatigued group. In a sample of patients comprised primarily of individuals with advanced colorectal cancer, Lundstom and Furst [41] found significant positive correlations between elevated cortisol levels, appetite loss, fatigue, and nausea/vomiting in a sample of palliative care patients, suggestive of an interaction between cytokines and the hypothalamic–pituitary– adrenal (HPA) axis. Under normal conditions, stressors
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induce an adaptive response to maintain homeostasis. In the presence of advanced cancer, however, we argue that the ability of the body to mount an adaptive response is challenged by disease processes as well as by any treatments including supportive care. Fatigue may thus be viewed as a behavioral marker for the body’s inability to adapt to these challenges.
Fatigue and muscle endurance We hypothesize that muscle endurance is a function of muscle mass, muscle strength, hemoglobin level, and inflammatory activity. Muscle mass and inflammation Many cancer patients experience a loss of muscle mass associated with muscle wasting. Tisdale [68] estimated that muscle wasting occurs in approximately 50% of all cancer patients. Most of this wasting occurs in skeletal muscle, appears to be due to accelerated muscle protein degradation, and is unresponsive to supplementary feeding [69]. This wasting is attributed in large part to the actions of a number of cytokines including TNF-α, IL-1, IL-6, and IFN-γ [3]. Muscle mass, muscle strength, and function Researchers in human body composition working with elderly populations found a clear relationship between sarcopenia [the loss of skeletal muscle mass greater than two standard deviations below the sex-specific mean for relative skeletal muscle index, muscle mass in kilograms divided by stature squared (kg/m2), in healthy young adults] and functional problems associated with gait, balance, risk of falls, and inability to complete tasks of daily living [8]. The limiting levels of skeletal muscle by these criteria are
