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