Rest/activity rhythm is related to the coexistence of pain and sleep disturbance among advanced cancer patients with pain

Purpose: This study aimed to explore the relationships among pain, sleep disturbance, and circadian rhythms in advanced cancer patients. Methods: This cross-sectional study was conducted in 68 cancer patients from the oncology inpatient unit of a teaching hospital. Their demographic and medical characteristics, questionnaire surveys, including Brief Pain Inventory-Chinese version and Pittsburgh Sleep Quality Index Taiwanese version, and sleep logs and actigraphic recordings in consecutive 3 days and nights were collected and analyzed. Results: The mean (SD) scores for autocorrelation coefficient at 24 h (r24) and dichotomy index (I<O) were 0.19 (0.16) and 85.29 % (0.13 %), respectively, indicating dampened circadian rhythms in participants. The mean (SD) worst pain score was 5.47 (2.70). The sleep quality global score ranged 4 ∼ 19 with a mean (SD) of 11.19 (4.05). The worst pain levels, the Pittsburgh Sleep Quality Index (PSQI) global score, and most sleep parameters measured by actigraphy were significantly correlated with r24 and I<O. The worst pain score was significantly correlated with the PSQI global score (r = 0.69, p < 0.01). The Goodman version of the Sobel test further demonstrated that 45.77 % of the total effect was mediated by pain intensity (t = 2.76, p = 0.005). Pain was a complete mediator between circadian rhythms and sleep quality. Conclusions: The rest/activity rhythm influences the coexisting pain and sleep disturbances. Pain functions as a complete mediator in their relationship. Interventions that improve rest/activity rhythms may improve the management of pain and sleep disturbances in cancer patients.