Cancer-related fatigue (CRF) is the most frequent and disturbing complaint of people with cancer. It is often defined subjectively as tiredness and lack of physical energy. CRF is a clinically defined multidimensional symptom resulting from the disease, the treatment, and the adverse effects of treatment. It can affect an individual’s relationships, daily activities, and economic state. 1–4 Sleep disturbances, or dyssomnias, are a related complaint and also a common symptom in people with cancer. These affect behavior, as well as neuroendocrine and central nervous system functions, and include sleepiness, hypersomnolence, narcolepsy, awakening during the night, or difficulty falling asleep. 1, 5–7 Although studies have examined CRF and sleep disturbances in the cancer population during or immediately after treatment, 5, 8–12 little research has explored survivors’ experience with these symptoms two years or more after diagnosis. This symptom dyad has also been associated with pain, anxiety, and depression, as well as with symptoms such as night sweats, hot flashes, diarrhea, constipation, and nighttime urination. 1, 3, 12–18 The complex relationship between CRF and sleep disturbances, as well as its relation to these other symptoms, has not been studied in long-term cancer survivors.
REVIEW OF THE LITERATURE
The databases Cumulative Index to Nursing and Allied Health Literature (CINAHL), PubMed, and ProQuest were searched for articles dealing with some combination of the following topics: fatigue, sleep disturbances including dyssomnia, and cancer including neoplasms. The Office of Cancer Survivorship Web site (http://dccps.nci.nih.gov/ocs) was also examined for funded projects that explicitly examined CRF and sleep disturbances. Four out of the 134 articles found addressed CRF and sleep disturbances specifically in long-term cancer survivors. 19–22
Three of the four studies found a statistically significant relationship between CRF and sleep disturbances (see Table 1, page 73). However, their design (survey) and their methodological limitations highlight the inadequacies of the research on the subject. For the most part, subjects were women with breast cancer from urban areas. The sample size for three of the four studies was relatively small, and there was limited representation from minority populations.
The study by Bower and colleagues represents the largest examination of fatigue in breast cancer survivors. 20 The authors reported that fatigue was not a significant problem for the majority of survivors, but that when present it was closely linked to depression and strongly associated with bodily pain and sleep disturbances. They further suggested that differing measurement techniques, sociodemographic characteristics of the sample, and geography may explain the differences between their findings and those of other published studies that reported CRF to be a significant problem for breast cancer survivors. 19, 21, 22 Most recently, Servaes and colleagues also found severe fatigue to be a problem for 40% of women breast cancer survivors who have completed treatment and otherwise returned to their normal lives. 22
RESEARCH, EDUCATION, PRACTICE, AND POLICY
CRF is a complex, multifactorial, and multidimensional clinical problem. Currently, there is no standardized method for measuring CRF. From a research perspective, it is important to conceptually define CRF and sleep disturbances and specify the measurement tools used in order to determine the comparability of the research findings. A fuller understanding of the phenomena can then allow a better description of their prevalence and inform tests of interventions and the development of evidence-based clinical practice guidelines for follow-up care and surveillance of long-term cancer survivors.
A better understanding of the relationship between CRF and sleep disturbances could further the knowledge about this symptom dyad as part of a symptom cluster that also includes pain, anxiety, and depression. Internal factors, both physiologic and psychological, and external environmental factors related to CRF and sleep disturbances in long-term cancer survivors are just beginning to be explored as causal, modifying, or associated factors. But still absent from the literature are the outcomes or consequences of CRF and sleep disturbances, such as irritability, lack of concentration, and difficulty making decisions, as well as their effects on the survivor’s life, including family, school, work, and social life.
Studying variables such as the economic consequences of fatigue on a survivor’s life and its effect on family caregiver issues would offer different insights and knowledge about CRF and sleep disturbances in long-term survivors. 23 Further research on the amount of fatigue survivors experience, the degree of distress it causes them, the effect of fatigue on activities of daily living, and the key biological parameters associated with fatigue can be translated into education and practice. For example, a test for determining whether fatigue is related to levels of specific cytokines in the body would allow clinicians to monitor fatigue, treat sleep disturbances, and possibly develop therapy to treat the fatigue. Measuring fatigue in a clinical setting, similar to clinical measurements of pain, could be useful in helping patients and survivors learn to self-monitor the symptom, seek help from occupational or physical therapists, or learn about exercises and activities that conserve energy. Assessing fatigue in relation to patient activities would allow clinicians to tailor exercise, work, and other activities to their needs.
Interventions such as walking exercise 24–26 and psychoeducational and structured educational programs 27 are proving to be effective in alleviating CRF and sleep disturbances with patients in active treatment and during the early posttreatment period. Testing the efficacy of such interventions in long-term cancer survivors may prove worthwhile. 25–29
Randomized controlled clinical trials that include interventions should also incorporate subjects of different ages and ethnic backgrounds, with different types of cancer and treatments, and at different points in the illness experience, including 10, 15, and 20 years or more into survivorship. Cooperative groups, such as the Eastern Cooperative Oncology Group and the Children’s Oncology Group, offer viable mechanisms for comprehensively surveying long-term cancer survivors. 3, 30, 31
Cancer-related fatigue and sleep disturbances must be considered as a clinical syndrome.
Clinical practice should involve assessing and identifying at-risk populations for CRF and sleep disturbances, and developing and testing effective interventions. CRF and sleep disturbances must be considered as a clinical syndrome. If these symptoms appear together—with or without concomitant symptoms such as pain, anxiety, or depression—they should be addressed clinically through ongoing assessment and adequate treatment plans, and the outcomes of cancer survivors should be evaluated. From a policy perspective, if a diagnosis-related group could be developed that included the sequelae of treatment, then the cost of screening for fatigue, sleep disturbances, and the myriad of other symptoms could be built into the health care system.
What to Ask Cancer Survivors
* Are you experiencing fatigue? If so, please describe.
* How would you rate your fatigue on a scale of 0 to 10, with 0 being no fatigue and 10 being the worst fatigue?
* How do you think that your fatigue affects your sleep or your sleep affects your fatigue?
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