Abstract
STUDY OBJECTIVES: Poor sleep quality affects nearly one-third of breast cancer survivors and is associated with insulin resistance. The purpose of this secondary analysis was to examine the effects of a 16-week exercise intervention on patient-reported sleep quality among breast cancer survivors and assess whether changes in patient-reported sleep quality were associated with cardiometabolic biomarkers. We explored Hispanic ethnicity as a moderator of the effects of exercise on patient-reported sleep quality. METHODS: Breast cancer survivors who were overweight or obese were randomized to exercise (n = 50) or usual care (n = 50). The 16-week intervention included aerobic and resistance exercise. Patient-reported sleep quality (Pittsburgh Sleep Quality Index [PSQI]) and biomarkers of cardiometabolic health were assessed at baseline and post-intervention. Within- and between-group differences were assessed using general linear models repeated-measures analyses of variance and mixed-model repeated-measure analysis, respectively. Associations between changes in PSQI and cardiometabolic biomarkers were computed using Pearson correlations. Linear mixed-models were used to evaluate effect modification by ethnicity. RESULTS: Participants were 52 ± 10.4 years old, and over half were of Hispanic ethnicity. As compared to usual care, PSQI global scores improved significantly in the exercise group (mean between-group difference -2.2; 95% CI -3.2 to -0.6). Change in PSQI was inversely associated with changes in all cardiometabolic biomarkers (p < 0.01) among the exercise group. Ethnicity was found to moderate the effects of exercise training on global sleep quality (p < 0.001). CONCLUSIONS: An aerobic and resistance exercise intervention effectively improved patient-reported sleep quality in breast cancer survivors. Hispanic ethnicity as a moderator showed greater improvement in patient-reported sleep indicating Hispanic versus non-Hispanic breast cancer survivors may derive larger sleep benefits. CLINICAL TRAIL INFORMATION: NCT01140282.