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Theories of Fatigue

Application in HIV/AIDS

Voss, Joachim G., PhD, RN; Dodd, Marylin, PhD, RN; Portillo, Carmen, PhD, RN; Holzemer, William, PhD, RN

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Journal of the Association of Nurses in AIDS Care: January-February 2006 - Volume 17 - Issue 1 - p 37-50
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Abstract

Infection with HIV-1 can ultimately lead to HIV disease and AIDS accompanied by a multitude of signs and symptoms. People with HIV/AIDS report fatigue to be one of the most frequent and distressing symptoms (Barroso, Carlson & Meynell, 2003; Breitbart, McDonald, Rosenfeld, Monkman, & Passik, 1998; Breitbart, Rosenfeld, Kaim, & Funesti-Esch 2001; Lee, Portillo, & Miramontes, 2001;Rabkin, McElhiney, Rabkin, & Ferrando, 2004; Vogl et al., 1999). Fatigue is discussed as a primary indicator for malfunctions of endocrine organs, muscles, and the brain (Dalakas, Mock & Hawkins, 1998; Noakes, St. Clair Gibson, & Lambert, 2004; Payne, 2004; Swain, 2000). Fatigue has been correlated with decreased quality of life, decreased functional status, and lower levels of adherence to highly active antiretroviral treatments (Crystal, Fleishman, Hays, Shapiro, & Bozzette, 2000; Duran et al., 2001; Henry, Holzemer, Weaver, & Stotts, 1999; Trotta et al, 2003). Most descriptive studies aim directly or indirectly at understanding the relationships between fatigue and its correlates. Only a small number of intervention studies focus on the improvement of fatigue in HIV (Breitbart et al., 2001; Gifford, Laurent, Gonzales, Chesney, & Lorig, 1998; Rabkin et al., 2004; Rabkin, Wagner, McElhiney, Rabkin & Lin, 2004; Wagner & Rabkin, 2000). Although there are a number of theoretical frameworks available, none of these theories have been used to guide intervention research for fatigue in HIV/AIDS. Are they too complicated or possibly too simplistic? Do they leave intervention outside their theoretical approach? Or is fatigue just too complex and multicausal to be explained within one framework?

To answer these questions, this report reviews two examples of theoretical frameworks (inductively and deductively derived) for fatigue and symptom management. A brief introduction into the discourse of theory-driven versus observational-driven theory development will help to clarify the major fundamental differences between the two exemplar theoretical models. Both models are reviewed and critiqued, and the results from the review provide suggestions as to how theories could help guide future clinical and interventional research to minimize fatigue. The complexity of HIV/AIDS in terms of diagnosis and treatment has stretched the boundaries of many disciplines including fatigue research. Besides nursing research-based fatigue models, a number of basic science models have been developed (neuroimmunology, neuroendocrine-based fatigue models, and circadian rhythm models). These will not be further discussed in this report because of its focus on nursing research; however, for an excellent review see Payne (2004) and Swain (2000).

Perspectives on Theory and Research

Ellis (1968) defined theory as “a coherent set of hypothetical, conceptual, and pragmatic principles forming a general frame of reference for a field of inquiry” (p.217). Chinn and Cramer (1991) applied Ellis's definition to their interpretation of research, theory, and practice. They stated that there is a reciprocal relationship between practice problems guiding theory development, theory development triggering new research questions, and research results potentially leading to the development of better theories.

In fatigue research, this would mean that we have a sufficient knowledge base of qualitative and quantitative studies that contribute to a general understanding of fatigue. This knowledge base would in reverse then contribute to fueling new research questions and theory developments and trigger outcomes-oriented research to prove the effectiveness of the theoretical assumptions.

Currently, most of the fatigue research in HIV/AIDS is deductive (general to specific). It is based on existing background literature and models from the cancer field that have been applied to develop theoretical frameworks. Less often, theoretical frameworks are built upon inductive observations from practice or research observations (specific to general). Independent of how the researchers came to their theoretical assumptions, the emerging concepts are the final building blocks of all fatigue theories. Assuming that these concepts and relationships are linked, they can be tested empirically. After empirical testing has proven significance between the concepts, investigators can apply this knowledge to evaluate the current theory, treatment development, and outcomes research. Along this process, Meleis (1997) proposed certain questions: “What specific theory propositions did the research consider? Were these central or peripheral propositions? Did research results contribute to the modification of an existing theoretical framework and broaden or limit its scope? Finally, did a theoretical framework provide validity of concepts or relationships to the research undertaken? Were explicit theory assumptions considered in designing methodology?” (p. 265).

This new information is assumed to be used in theory, research, and/or practice where it can be applied. However, in nursing research, the relationship between theory, research, and practice has traditionally been difficult and independent of their benefits to each other. Research results transferred into practice are associated with change of routines and habits and that which is most often inconvenient and causes resistance (Higginson, 2004; Roe et al., 2004).

The fatigue models that are based on inductive observations focus on the observation of a particular phenomenon; for example, an intervention that proved to be successful to decrease the perception of fatigue. These inductive observations are then the basis for the development of the theoretical model, future research questions, and concurrent interventions. An example of inductive research is a community-based sample of healthy women who were found to have internal demands that were more predictive of fatigue than their external social and role demands (Lee, Lentz, Taylor, Mitchell & Woods, 1994). Winningham et al. found consistently across groups of women with breast cancer that their fatigue ratings decreased over time when they participated in an exercise intervention (Winningham, 1991b; Winningham & MacVicar, 1988; Winningham, MacVicar, Bondoc, Anderson, & Minton, 1989). The investigators designed a theoretical framework from their results to guide further research into the severity and distress of fatigue, to investigate the effectiveness of exercise as an intervention for fatigue, and to reject current medical paradigms that rest while on cancer treatments is beneficial for fatigue. Evidence from the past decade supports positive outcomes of theory-based exercise interventions (Piper, Lindsey, & Dodd, 1987; Schwartz, 2000; Winningham, 1991a, 1991b, Winningham & Barton-Burke, 2000). The experiences of these investigators were suggestive to apply the theory base on fatigue and exercise to an HIV population. Around 25 trials have been conducted with aerobic and resistance exercise interventions, and results were mixed. (For a review see Ciccolo, Jowers, & Bartholomew, 2004; and Dudgeon, Phillips, Bopp & Hand, 2004.) Although some trials showed improvement, others showed an increase in fatigue. Obviously, the perception of “fatigue is fatigue is fatigue” is incorrect, and what was a successful intervention in one population might be harmful in another.

However, even when theories have not reached the level of sophistication we would like them to have, in general, they can be guidelines for researchers and clinicians in developing new ways of investigating and understanding fatigue in HIV/AIDS. In fatigue research, many facts continue to be unknown, and ongoing research needs to continue to elucidate a better understanding of the concepts. Two current theory models as described later have been partially tested in a small number of studies, which could be indicators that fatigue in HIV has a theoretical complexity that is not easy to grasp. The challenge is not to look only for causal relationships between a symptom and its treatment but to focus simultaneously on the influences of cultural backgrounds, different health beliefs, or the contribution of the mind-body connection in the management of a specific symptom.

In summary, the complexity of the symptomatology of fatigue in HIV disease and the development of a research-based theoretical framework would be beneficial to guide future fatigue research. Otherwise, we would lack scientific proof of the methods of to assess fatigue or in the types of interventions resulting in inconsistent study outcomes. Analysis and critique of the theoretical frameworks would require continuous examination to integrate new results and adjust them for use in HIV/AIDS patients suffering from or at risk of fatigue.

Brief Review and Critique of Current Fatigue Theories

Although it seems appropriate, this report does not attempt to review all of the existing fatigue models (Barroso, 1999); however, some of the best known models are mentioned briefly. For an excellent review see Aaronson et al. (1999) and Payne (2004). The conceptualization of energy and fatigue has triggered a number of fatigue theories such as Aistairs' organizing framework (1987), Irvine, Vincent, Graydon, Bubela, and Thompson's energy analysis model (1994), Piper et al.'s integrated fatigue model (1987), Lee et al.'s fatigue and women's health model (1994), and Winningham's psychobiological entropy model (1996). Ream and Richardson (1999) summarize these models as being practice-oriented and rated the theories to be limited in their predictive capacity (Ostrop, Hallett, & Gill, 2000; Tsevat et al., 1996), but they would offer tentative guidelines for clinical practice and directions for research (Ream & Richardson, 1999). Despite criticism by Ream and Richardson (1999), Piper's integrated fatigue model (IFM) offers a theoretical framework and a validated measurement tool that has been developed for use in breast cancer patients and applied to various patient populations (cancer, end-stage renal disease, HIV/AIDS, postpolio syndrome), which increases its credibility to be used as a framework for fatigue research across a broad spectrum of diseases Breitbart et al., 2001; Cho & Tsay, 2004; Phillips, et al., 2004; Strohschein et al., 2003; Trask, Paterson, Esper, Pau & Redman, 2004). The following section will review one of the more frequently cited theories on fatigue, the IFM, and a much broader theory on symptom management, the University of California, San Francisco Symptom Management Model (UCSF-SMM) for their applicability to a better understanding of fatigue in HIV.

The Integrated Fatigue Model

A team of nurse scientists led by Barbara Piper developed the IFM in the 1980s deductively from a review of the literature on cancer fatigue (Piper, 1993; Piper et al., 1987). It is a comprehensive framework that describes 14 biological and psychosocial patterns that influence signs and symptoms of fatigue in clinical populations, specifically women with breast cancer. The developers understood the wide range of contributing factors to be interrelated to each other, which leads to chronic fatigue experiences for cancer patients. In addition, the IFM indirectly gives multiple possibilities on how fatigue can be manifested and provides a base for the assessment of nursing practice. The IFM is currently the only model proposed for guiding fatigue research in HIV/AIDS and in the investigation of the multiple contributing factors. The model is based on the definition that fatigue in HIV/AIDS is a perception of unusual or abnormal whole-body tiredness disproportionate to or unrelated to activity or exertion. Fatigue cannot be resolved with sufficient sleep or rest. It is termed acute when experienced for less than a month and chronic when experienced for more than one month (Piper, 1993).

According to Piper (1998), fatigue in HIV/AIDS is experienced on six dimensions: temporal (circadian differences), sensory (intensity and local or systemic symptoms of fatigue), cognitive/mental (alteration in memory, concentration, attention, and alertness), affective/emotional (increasing irritability, impatience, lack of motivation, depression), behavioral (impact on activities of daily living), and physiological (changes in laboratory, radiographic, and physical exams). One or more patterns (recurring characteristics over time for a specific individual) can influence each fatigue dimension. There are 14 types of patterns and 6 fatigue dimensions depicted in Figure 1. The figure lists the unidirectional factors that influence the experiences of fatigue in cancer and in HIV/AIDS (Piper, 1993, 1998) posited to contribute to fatigue in HIV. The following paragraph describes examples of theoretically derived relationships as proposed in the IFM model.

Figure 1
Figure 1:
The Integrated Fatigue Model. Modified with permission fromPiper, B. F. (1998). Fatigue. In M. E. Ropka, & A. B. Williams (Eds.), HIV nursing and symptom management. Boston: Jones and Bartlett, p. 451.

The prevalence of anemia in HIV ranges from 70% to 90% (Wilson & Cleary, 1996). In addition, the complications of HIV-related lung disease (Murray, 1996; Rosen, 1996; Schneider & Rosen, 1997) support the relationship to oxygenation patterns. An increase in lactate dehydrogenase, for example, in Pneumocystis carinii (Darko, McCutchan, Kripke, Gillin, & Golshan, 1992) supports the theoretical relationship between the accumulation of toxic metabolites and fatigue. Progressive wasting, weight loss, and altered nutrition (Parisien, Gelinas, & Cosette, 1993), elevated total globulin levels (total protein minus albumin) (Darko et al., 1992), and increased resting energy metabolism support the theoretical link between fatigue and energy substrates. Empirical results regarding decreased motor functioning (Perkins et al., 1995) and decreased functional status (O'Dell, Hubert, Lubeck & O'Driscroll, 1996) support the theoretical relationship between fatigue and activity/rest patterns. Insomnia and sleep patterns (Darko et al., 1992; Lee, Portillo, & Miramontes, 1999, 2001) support the theoretical relationship between fatigue and altered sleep/wake patterns.

Results showing an association between lower CD4+ cell counts and increased fatigue levels (Darko et al., 1992; Lee et al., 1999, 2001) support the theoretical relationship between fatigue and disease severity. Zidovudine-induced anemia (Fischl, 1989; Fischl et al., 1989) and mitochondrial toxicity (Darko et al., 1992) support the relation to treatment strategies. Pain, diarrhea, and night sweats established the relationship between increased number and distress of symptoms and symptom patterns (Lubeck & Fries, 1993; Wilson & Cleary, 1995).

The IFM model posits that psychological patterns are linked to fatigue. Anxiety, depression, lack of motivation, and metal health problems (O'Dell, Meighen, & Riggs, 1996; Perkins et al., 1995; Wilson & Cleary, 1995) are common in HIV and are associated with fatigue. Adrenal insufficiency (Kaplan et al., 1987); elevation of humoral mediators such as interferon, tumor necrosis factor, interleukins (Piper, 1993); and electrolyte imbalances (Yu-Yahiro, 1994) provide evidence for a relationship with metabolic regulation and transmission. Environmental factors such as exposure to noise, heat, allergens, and altitude (Piper, 1993) and social factors such as cultural and ethnic practices (Piper, 1993), sexual preferences, and drug abuse patterns (Palenicek et al., 1993) support the relationship to environmental patterns. Significant life events are posited to be associated with fatigue, and the documented changes in the lives of people with HIV/AIDS such as loss of a job, relocation to a new city, loss of friends, and grief support the relationship to social patterns (Piper, 1993). Finally, differences in innate host factors such as age, gender (Semple et al., 1993), race, and genetic makeup (Piper, 1993) would support the innate host patterns.

Many of these original references seem to be outdated; however, a large number of the relationships Piper proposed have been confirmed by multiple investigators. Therefore, Piper has significantly contributed to the discourse and the theoretical development of fatigue in HIV/AIDS. Yet Piper has been criticized for not testing these proposed relationships in an HIV population. Some of the proposed factors reflect the knowledge of the early to mid 90s and have not been currently updated. Finally in 2004, Phillips et al. based their study on Piper's framework to test associations of physiological, psychological, and sociological factors with fatigue in a sample of men and women with HIV/AIDS (N = 79). They found significant relationships between fatigue and sleep quality, daytime sleepiness, HIV-related symptoms, state anxiety, trait anxiety, depression, and perceived stress.

One criticism of the model is that the 14 factors influence to some degree the fatigue experiences of people with HIV, but they are not organized into a system by the distress they cause or by any hierarchy. The IFM allows selection of certain patterns and investigation of one or multiple relationships between the patterns and the symptom dimensions. Each pattern and its relationship with the fatigue dimensions generates a multitude of potential causal hypotheses.

The IFM fails, however, to indicate which of the patterns are interrelated, whether there is a reciprocal relationship between causal patterns and certain fatigue dimensions, and if the patterns can be weighted or hierarchically ordered (Winningham et al., 1994, Winningham & Barton-Burke, 2000). Therefore, the IFM generates unidirectional and testable hypotheses but provides limited guidance for strategies to reduce or manage fatigue because interventions and outcomes are not integrated into the IFM.

The Revised Symptom Management Model

The UCSF-SMM is not a fatigue-specific model but is more a multidimensional symptom management model that is embedded within three nursing domains: person, environment, and health and illness (Dodd et al., 2001, Larson et al., 1994). The system was developed by a number of scholars at the University of California, San Francisco, School of Nursing, Center for Symptom Management and is the result of ongoing research on the model. The UCSF-SMM consists of three inner circles with spheres interacting between symptom experience and symptom management strategies (process), and the third circle with its potential outcomes to consider in addition to a change in the severity, frequency, or duration of the symptom. This interdependent process of symptom management is placed within three domains of nursing that interact with each other (see Figure 2). The person dimension represents all of the individual variables that influence symptom management the environment represents all of the social and cultural variables, and finally, health and illness represents the risk factors for the symptom such as injury or infection.

Figure 2
Figure 2:
The Revised University of California, San Francisco, Symptom Management Model. Reprinted with permission fromDodd, M., Janson, S., Facione, N., Faucett, J., Froehlicher, E. S., Humphreys, J., et al. (2001). Advancing the science of symptom management. Journal of Advanced Nursing, 33(5), 668–767.

The model is based on the following six assumptions:

  • Gold standard is the self-reported symptom experience of the patient.
  • Presence of a symptom is not required for the applicability of the model. The risk for developing a symptom is a reason for the initiation of interventions before individual symptoms can be experienced.
  • Nonverbal patients experience symptoms, and symptom interpretation by family members and caregivers is assumed to be accurate for symptom management.
  • Management strategies can be targeted toward the individual, groups, a family, or the work environment.
  • Symptom management is a dynamic process that is modified by individual outcomes and environmental influences.

Model Components

Person domain

The person's views and responses to the symptom experience uniquely define demographic, physiological, psychological, and sociological person-variables. Developmental variables encompass the level of maturity of an individual. Depending on the focus, symptom, or population of interest, the person-variables can be limited or expanded. Lee and Taylor (1996) documented in midlife women that fatigue has an impact on the developmental stage, when menopausal symptoms affect the quality of sleep. Rankin demonstrated in two studies (1990, 1992) that gender affected cardiovascular outcomes in women with coronary artery bypass graft surgery and that women after myocardial infarction experienced higher morbidity and mortality.

Health/illness domain

Health and illness variables are unique to the states of health and illness of an individual and include risk factors, injuries, and disabilities. Janson and Carrieri (1986) found that different types of pulmonary diseases produced quantitatively and qualitatively different symptom experiences (Janson, Covington, Fahy, Gold, & Boushey, 1999). The type and extent of cancer determined treatment choices (Facione, Misakowski, Dood & Paul, 2002), and in terms of received treatment affected risk factors for related morbidities (Dodd et al., 1999).

Environment domain

Symptoms occur in a specific environment and include physical, social, and cultural variables. The home, work, or hospital is an example of physical environment in which social networks and interpersonal relationships are part of the social environment. Cultural aspects of an environment are beliefs, values, and practices defined in part by one's ethnic, racial, or religious group. Humphreys, Lee, Neylan, and Marmar (1999) and Humphreys (2003) reported that being temporarily sheltered because of domestic violence had a significant impact on women's perceptions regarding fatigue and sleep. Asthma patients who were taught self- management in individual sessions had better adherence to therapy and improved medication skills than those taught in groups (Janson et al., 1999, 2003). These three nursing domains of person-environment-health/illness underlie the entire model, whereas the symptom experience, symptom management strategies, and outcomes are the central elements of the model.

Symptom experience

Symptom experience can be divided into symptom perception by the individual, evaluation of the meaning of the symptom, and reaction or response to the symptom. The perception of fatigue, for example, depends upon one's state of alertness but also on the judgment of everyday perceptions and feelings. The symptom is evaluated by judging the severity, cause, treatment options, and effects on quality of life or daytime functioning. Responses to fatigue can be multidimensional and include physiological, psychological, sociocultural, and behavioral components (Aaronson et al., 1999; Belza, 1995).

Symptom management strategies

Symptom management is necessary to prevent or manage negative health outcomes through professional and self-care strategies. Identifying the focus for interventions follows assessment of fatigue. Interventions target one or multiple symptoms and try to achieve the desired outcome. This process is dynamic and requires frequent changes in strategies because of response or lack of acceptance and adherence. These strategies are defined by the questions on what, when, where, why, how much, to whom, and how these interventions will be delivered.

Symptom outcomes

Desired outcomes simultaneously emerge from management strategies and from the symptom experience. In addition to improvement of symptom status, evaluation of outcomes needs to be considered and measured, such as functional status, emotional status, mortality, morbidity/comorbidity, quality of life, and costs. These broader based outcomes factors need to be understood in relation to each other as well as to the symptom status or pattern.

The application of the current knowledge on fatigue in HIV into the UCSF-SMM offers systematic understanding of current research results, and it offers directions for future research. In the person domain, individual (person) variables may influence the level of fatigue in HIV/AIDS patients including age (Singh, Squier, Sivek, Wagener, & Yu, 1997), gender, ethnicity (Voss, 2005), income, educational background, coping styles, and so on. In our study with HIV/AIDS outpatients in Texas (N = 372), we found that educational background was an independent predictor of physical health and fatigue (Voss, 2005). The interaction between the person domain and the health and illness domain is the location to integrate the complex interplay of stress-psychoneuroimmunology and HIV (Antoni, 2003). The health and illness domain includes the symptom burden of the HIV disease itself and risk factors such as addiction, presence of opportunistic infections, possible side effects of treatments, and present or developing comorbidities. The environment domain encompasses the work, home, and hospital influences; the impact of social networks; and culture-specific beliefs, values and practices associated with fatigue. The symptom experience circle includes measurement issues of fatigue in HIV (Aaronson, et al., 1999), as well as other associated symptoms of fatigue such as pain, insomnia, and depression. The symptom management circle encompasses interventions such as testosterone supplementation, physical exercise, and psychostimulants that have been investigated to decrease fatigue. The outcome circle includes the concepts that provide opportunities to evaluate the effectiveness of interventions for the patients as well as for society.

Each circle provides a unique opportunity for the next generation of research questions to be asked. In the person circle, one could hypothesize that age is a contributing factor that increases fatigue in people with HIV/AIDS secondary to a hormonal imbalance caused by HIV-induced damage in the hormone producing glands and the brain. Other areas of interest could be the following:

  1. Where is fatigue perceived (brain or muscle)?
  2. How is fatigue perceived (chemical imbalances or psychological perception)?
  3. What role do cytokines play in the fatigue perception?
  4. How is HIV-related fatigue different from fatigue perceived after a marathon (mitochondrial intoxication or exertion)?
  5. How do patients adjust to various fatigue levels?
  6. Are fatigue levels comparable between groups, ages, or genders?

There are open questions in the health and illness domain: Which risk factors actually contribute to higher levels of fatigue? What are health behaviors that prevent fatigue? While progress has been made in the measurement of perception of fatigue, little is known about how symptoms are evaluated by the individual. The same is true for the responses to symptoms. Does severity, duration, or quality of fatigue influence the evaluation or response to interventions? Thus far, these areas are insufficiently explored. Interventions relevant to fatigue received increasing interest in the last couple of years and will be an important field of research. Results will impact clinical practice of healthcare providers. The effectiveness of self-care strategies across populations and the costs of fatigue caused by disability are a few of the unknown issues reflected in the symptom outcome circle. Little is known about how fatigue and targeted interventions influence mortality and morbidity or how an intervention can enhance long-term functional or emotional status.

The UCSF-SMM is presently one of the most elaborate models for symptom management. It is applicable not only to fatigue in HIV but to all symptoms of healthy and ill people. It can be a guiding framework for future research on fatigue in HIV. The UCSF-SMM is still an evolving model, and some issues need to be investigated further; for example, how to study simultaneously occurring symptoms or symptom clusters. Currently, the model focuses on the patient's primary symptoms (like fatigue), but with symptom clusters, the symptom in the forefront could move to the background and other symptoms (such as depression, neuropathy, and insomnia) become more or less severe or distressing.

Summary and Discussion

The IFM depicts linear relationships between fatigue experiences in HIV and theoretically derived causes. The UCSF-SMM is a multidimensional, interactive, process-oriented model derived from research in various aspects of symptom management. The model presented by Piper et al. was an important development for the understanding and explanation of fatigue in women with cancer and was extended to other types of cancer and HIV/AIDS. Only steady progress on the issues of fatigue in cancer helped to shape the understanding of the complex cancer-related fatigue syndrome. Piper was a pioneer in providing a theoretical explanation and introducing a universal model for fatigue in cancer, which later was extended to HIV/AIDS. The IFM integrated research results regarding HIV/AIDS that provided evidence that links key concepts in HIV disease and fatigue. However, because of its linear nature, the model does not reach the level of guidance necessary to take theory development or research on fatigue in HIV/AIDS a significant step forward. This is because the model describes the phenomenon and does not provide directions for interventions.

The UCSF-SMM evolved over the last decade from research results by scholars at UCSF, San Francisco, School of Nursing, Center for Symptom Management. It is a conceptual model based on the three nursing domains (person, environment, health and illness) that interact with symptom experience, management, and multidimensional outcomes. In this model, symptom management can be focused on healthy or ill people, children or adults, or the caregiver, as well as on the patient, and can be applied to different demographic or cultural populations. Because of the flexibility of the model (not disease-focused) it can be applied to diverse clinical populations or healthy individuals. The UCSF-SMM is directional in that it begins with the symptom experience of the person or their family and caregivers. These perceptions initiate a cascade of following actions, interactions, and results. Similar to the nursing process, which includes data collection, goal definition, intervention planning, and evaluation, the UCSF-SMM has these repetitive circles of perception-management-outcomes that are complete only if the symptom is well-managed. The strength of this model is its ability to offer researchers and clinicians a clear understanding of symptoms through the feedback of their patients and their environment. However, the multitude of influential factors in this model is also one of its weaknesses. The complexity can be overwhelming for an investigator trying to decide which variables to select for a study. Therefore, use of smaller parts of the UCSF-SMM provides an excellent guideline for complex relationships and interdependencies between the nursing domains and the symptom concepts.

Virtually, the IFM could be incorporated within the UCSF-SMM. The fatigue dimensions of the IFM, for example, represent the symptom experience in the health and illness domain of the UCSF-SMM. The social, life event, environmental, and innate host patterns of the IFM represent the environment domain in the UCSF-SMM but do not represent the symptom management strategies circle. The other patterns of the IFM can be found within the person domain of the UCSF-SMM but do not represent the factors in the outcomes circle. Table 1 conceptualizes the present knowledge about fatigue in HIV into the symptom management model and possible areas of intervention research.

Table 1
Table 1:
The University of California, San Francisco Symptom Management Model and Fatigue in HIV/AIDS

The UCSF-SMM is presently one of the leading theories for nursing research on fatigue in HIV, because it focuses not only on the individual level of the patient but takes contextual and health/illness perspectives into account as well. It qualifies as a middle-range theory because of its wide conceptual range and ability to generate a plethora of working hypotheses. The theory is abstract enough to extend beyond a given place, time, and population but specific and sufficiently close to test and generate distinct questions for investigations or interventions (Walker & Avant, 1995). With its use, a multitude of research possibilities evolve. This process will help to determine whether fatigue is a symptom or a syndrome, and if it is a syndrome, which other symptoms accompany fatigue in HIV. The answers to these questions are found in the future research efforts of a number of disciplines, one of which is nursing. Collaborative efforts will be necessary to understand the personal experience of fatigue, the complex interplay between the immune system and the brain, antiretroviral treatment effects in the human body, and the social and political influences.

Future of Theory Development in HIV/AIDS Fatigue

J. Barroso, a fatigue researcher in HIV/AIDS, is conducting an ongoing study until 2007 to validate the first HIV/AIDS-specific fatigue model (personal communication, March 10, 2005). This model is based on existing fatigue research results and Barroso's own four preliminary studies (Barroso, 2002; Barroso et al., 2002; Barroso & Lynn, 2002; Barroso et al., 2003). The model displays the anticipated relationships among the variables to be studied (see Figure 3). The four broad areas that may influence HIV-related fatigue are personal, HIV-related, physiological, and psychosocial variables. In figure 3, the variables to be measured in each of these areas are shown outside of the circle, with the gray arrows indicating whether an increase or decrease would be expected to increase HIV-related fatigue. For some personal and HIV-related variables, existing research is conflicting; these are marked with question marks as unknown. Finally, sleep quality is presented between physiological and psychosocial variables, because poor sleep can result from factors in each of these areas. The trajectory at the bottom of the figure represents the changes over time that will be observed. The authors anticipate the usefulness of the refined model and look forward to the completion of the validation study.

Figure 3
Figure 3:
Multidimensional Model of HIV-Related Fatigue. Reprinted with permission from Dr. Julie Barroso, Assistant Professor, Duke University, Durham, NC.

Acknowledgment

Special thanks to Dr. Katherine Lee for her thoughtful review of this article.

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    Keywords:

    HIV; fatigue; theories; research; practice; nursing

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