Sleep problems are a common complaint in cancer patients. Descriptive reports indicate that 20–70% of women with breast cancer (BC), and 30–50% of men with prostate cancer (PC) report having sleep difficulties at some point during the cancer trajectory [1
]. Cross-sectional studies have documented sleep problems before, during, and after treatment with different modalities, including radiation, chemotherapy, and surgery [3
]. Additionally, sleep problems are correlated with impairments in quality of life, and may also contribute to other behavioral co-morbidities that afflict cancer patients [4
]. Research suggests that among patients with cancer, sleep disturbance is associated with greater intensity of fatigue, more anxiety and depressive symptoms, and poor social functioning [4
Despite growing interest in sleep, relatively few studies have examined sleep complaints as a primary outcome of interest in individuals with cancer. In particular, longitudinal studies that attempt to identify the phase at which sleep begins to deteriorate in these patients have been scarce. Of the longitudinal studies published in this area, most have been conducted with BC patients undergoing chemotherapy. These studies have found worse sleep in BC patients during chemotherapy than prior to treatment [13
]. Additionally, BC patients who undergo chemotherapy report some improvement in sleep 30 days after treatment has been completed [16
]. However, more research is needed to understand whether sleep problems persist long after treatment has ended when patients are coping with longer term side of the disease and treatment.
To our knowledge, no published study has examined longitudinal changes in sleep in PC patients, the most common cancer diagnosed in men. Additionally, no longitudinal studies have examined changes in sleep among cancer patients undergoing radiation therapy. The lack of longitudinal research in these patients limits our ability to discern whether sleep difficulties are the same in patients with different forms of cancer as well as those who undergo different treatment modalities. This information is crucial in order to identify potential causes of sleep problems, information that is necessary for developing appropriate treatments.
There is also a lack of information about factors that may influence cancer-related sleep problems. Psychosocial factors may play a major role in determining who is at greatest risk for developing sleep problems in response to cancer; indeed, psychosocial variables were shown to be the strongest predictors of insomnia in a large study of breast cancer survivors [17
]. However, we currently know very little about specific psychosocial predictors of sleep in cancer patients. Research on psychological adjustment to cancer diagnosis and treatment suggests that coping processes are important predictors of recovery. For example, cancer patients who use more approach coping strategies report better psychological adjustment [18
], whereas engaging in more avoidant coping strategies is associated with distress during and after treatment [21
]. A similar pattern of results has been found in other clinical populations, with approach coping strategies being associated with less depression and anxiety as well as better health outcomes [23
] Use of maladaptive coping strategies has been shown to predict cancer-related fatigue in breast cancer patients [24
]. However, to our knowledge, no studies have examined the impact of coping processes on sleep within the context of cancer.
The primary goals of this longitudinal study were to 1) evaluate changes in sleep over the course of treatment and follow-up in patients undergoing radiation therapy for BC or PC and 2) to determine whether coping strategies (approach and avoidance) influenced sleep trajectories in these patient groups. We focused on breast and prostate cancer patients as these are the most prevalent types of cancer among women and men in the US. Several dimensions of sleep were assessed in the current study using the Medical Outcomes Study (MOS) Sleep Scale. These included difficulty falling asleep and maintaining sleep, sleep adequacy, sleep quantity, and overall sleep problems.
Sleep was examined at 8 assessment points scheduled at specific intervals before, during, and after treatment. Based on cross-sectional findings that BC and PC patients report poor sleep during treatment [1
] and that sleep difficulties remain a problem after treatment has been completed [10
], we expected that problems with sleep would develop over the course of treatment and that these sleep problems would remain a significant problem during post-treatment evaluations.
Coping strategies were assessed at baseline and examined as predictors of sleep over time in both BC and PC patients. To date, no published study has examined the impact of coping strategies on trajectories of sleep over the course of treatment and follow-up. Thus, this is a novel aspect of the current study. Based on research suggesting that approach coping is associated with well-being in cancer patients [19
], we hypothesized that patients who used approach-oriented coping strategies would report fewer sleep problems over the course of treatment and follow-up, whereas those high in avoidance coping would report more sleep problems. All hypotheses were tested using mixed effects linear modeling.