Consistent with prior research, our findings supported the hypothesis that patients with breast cancer undergoing chemotherapy report higher levels of sleep disturbance than those not undergoing treatment. We also concluded that patients with breast cancer undergoing radiation report higher levels of sleep disturbance than those not undergoing treatment, although the level of subjective sleep disturbance is similar between those undergoing chemotherapy and radiation. While a prior study found that insomnia was more likely to be discussed with patients at appointments with a transplant team or medical oncologists, when compared to other provider teams [28], this finding highlights the need for all providers, including radiation oncologists, to assess sleep disturbance in their patients, as it may be associated with a variety of treatments.
Other studies have suggested that sleep disturbance may occur in a symptom cluster along with fatigue and pain [4], as well as in conjunction with a variety of other symptoms including the severity of depressive symptoms, anxiety, and nausea, and decreased quality of life [10-13]. For women receiving radiation, sleep disturbance was associated with pain, pain interference, nausea, anxiety, depressive symptoms, fatigue, decreased physical function and decreased ability to participate in social roles, indicating a central role for sleep disturbance in symptom burden for this population. The large number of co-occurring symptoms for the women in the radiation group highlights the need for overall symptom control.
In the women undergoing adjuvant chemotherapy, sleep disturbance was only associated with higher levels of anxiety and depressive symptoms as well as lower ability to participate in social roles. This indicates the possibility for a different underlying mechanism of sleep disturbance in women receiving chemotherapy, and the potential need to focus on the impact of psychological and social factors associated with chemotherapy treatment as they affect symptom development.
In women undergoing AI therapy, sleep disturbance was only associated with fatigue. Given that AI therapy is associated with menopausal symptoms such as hot flashes [29], it is possible that co-occurring symptoms in this group were not captured by this study. In participants receiving no adjuvant therapy, sleep disturbance was associated with pain, pain interference, nausea, fatigue.
The difference in symptoms co-occurring with sleep disturbance among treatment groups suggests that etiology of sleep disturbance may differ across treatment groups, and interventions for sleep disturbance may need to be tailored to both treatment modality and associated symptoms.
These associations between sleep disturbance and other symptoms including pain, nausea, depression, anxiety, decreased physical function and difficulty participating in social roles and activities, especially in the radiation group, suggest the need for investigation regarding how symptom burden may be treated in a holistic manner. While some research indicates that there is no clear evidence that treatment of one facet in the fatigue-depression-sleep disturbance symptom cluster is effective in mitigating other symptoms [30], other research suggests that therapy intended to relieve a single symptom, such as anxiety or depression, may be useful in relieving sleep disturbance [31]. However, recent clinical practice guidelines on the use of integrative relief for symptom burden in cancer using review of recent literature lists yoga as the only integrative therapy recommended for sleep disturbance [32]. The results of our analysis linking sleep disturbance to other symptoms suggests that the treatment of sleep disturbance may be a step towards a holistic approach to relieving symptom burden.
Our analysis supported the finding that sleep disturbance in patients with breast cancer is associated with younger age. However, in contrast to former literature, no association was found between BMI and reported sleep disturbance.
A limitation of this study was the relatively low number of minorities included in the analysis. Given the evidence on disparities in treatment for sleep disturbance in this population, care should be taken to describe the symptom experiences of minorities going forward.
Another limitation of this study was the lack of objective sleep data. Prior research using both objective and subjective sleep data in this population has found discrepancies in the two sources of sleep data [33-34], with one study finding no differences in electroencephalogram parameters between breast cancer patients who reported insomnia and those who did not [35]. Given the discrepancies between objective and subjective data on sleep disturbance in this population, caution must be used when applying the results of this analysis to objective sleep quality. The focus of the results of this study is on the patient reported outcomes regarding sleep disturbance symptoms.
Given the cross-sectional design of this analysis, future research should measure changes in sleep disturbance over time in this population, and how it may be confounded by treatment factors. Investigation into how sleep disturbance may change over the course of treatment in this population would be informative given recent research suggesting that patients with relatively low or high sleep disturbance severity before chemotherapy treatment tend to remain in the same severity group at the end of treatment [36].
Patients undergoing breast cancer treatment should be thoroughly evaluated for sleep disturbance. The association of sleep disturbance with other symptoms, including pain, nausea, anxiety, depression, decreased physical function, and difficulty participating in social roles, indicates sleep disturbance’s role as an integral player in the symptom burden associated with breast cancer diagnosis. Treatment of sleep disturbance should be considered as a method to alleviate symptom burden in this population.