The influence of yoga on mediational relationships between sleep and cancer-related fatigue: A URCC NCORP RCT in 321 cancer patients.

Abstract

10007 Background: Cancer-related fatigue (CRF) is one of the most incapacitating adverse effects of cancer and its treatments. CRF co-occurs with impaired sleep quality in cancer survivors, increasing morbidity and mortality. We have previously shown that yoga significantly lowers CRF and improves sleep quality in survivors. However, it is not clear if the effect of yoga on CRF is mediated by improvements in sleep quality. This study assessed the mediating effects of changes in sleep quality stemming from YOCAS yoga on improvements in CRF. Methods: We conducted a secondary analysis on data collected from a multicenter phase III randomized controlled clinical trial with 2 arms (standard care and standard care + a 4-week YOCAS yoga intervention). 321 cancer patients (96% female; mean age, 54 years; 77% had breast cancer) reported both sleep quality, measured by the Pittsburgh Sleep Quality Index (PSQI), and CRF, evaluated by Multidimensional Fatigue Scale Inventory (MFSI). Causal mediation analyses were used to estimate effects of the changes in global PSQI scores and in each PSQI subscale on the relationship between yoga and CRF. Results: Yoga significantly improved both CRF (p < 0.01) and sleep quality (p < 0.01), compared to standard care, with total reduction in CRF by 6.5 points. Sleep quality significantly mediated the changes in CRF by 1.4 points (p < 0.01) in addition to the direct effect of yoga on CRF reduction (by 5.1 points; p < 0.01), suggesting that 22% (95% CI: 7%-54%) of the reduction in CRF was mediated through improving sleep quality. Among the PSQI subscales, daytime dysfunction had the most mediating effect of yoga on CRF. In this model, yoga directly improved CRF by 4.1 points (p = 0.01) and the mediating effect of yoga on CRF via daytime dysfunction was 2.4 points (p < 0.01), suggesting that 37% (95% CI: 23%-81%) of the improvements in CRF was mediated through decreasing daytime dysfunction. Conclusions: Between 22 and 37% of the improvements in CRF from yoga are due to improvements in sleep quality and reductions in daytime dysfunction. Clinicians should consider prescribing yoga for survivors experiencing CRF in combination with sleep disorders. Funding: NCI UGCA189961, R25 CA102618. Clinical trial information: NCT00397930.