Sedentary behavior, health-related quality of life, and fatigue among breast cancer survivors.

BACKGROUND Many cancer survivors experience declines in health-related quality of life (HRQOL) and increases in fatigue as a result of cancer and its treatment. Exercise is linked to improvements in these outcomes, but little is known about the role of sedentary behavior. In a large, ethnically-diverse cohort of breast cancer survivors, we examined the relationship between sedentary time, HRQOL, and fatigue, and examined if that relationship differed by recreational moderate-vigorous physical activity (MVPA) level. METHODS Participants were 710 women diagnosed with stage 0-IIIA breast cancer in the Health, Eating, Activity, and Lifestyle Study. Women completed questionnaires at approximately 30-months postdiagnosis (sedentary time; recreational MVPA) and 41-months postdiagnosis (HRQOL; fatigue). In multivariate models, we regressed these outcomes linearly on quartiles of daily sedentary time, and a variable jointly reflecting sedentary time quartiles and MVPA categories (0; >0 to <9; ≥9 MET-hrs/wk). RESULTS Sedentary time was not independently related to subscales or summary scores of HRQOL or fatigue. In addition, comparisons of women with high vs. low (Q4:Q1) sedentary time by MVPA level did not result in significant differences in HRQOL or fatigue. CONCLUSION In this breast cancer survivor cohort, self-reported sedentary time was not associated with HRQOL or fatigue, 3.5 years postdiagnosis.