Abstract
PURPOSE: This study examined relationships between sedentary behavior accumulated in different bout durations and quality of life (QoL) among breast cancer survivors. METHODS: Postmenopausal breast cancer survivors completed the Short Form Health Survey to assess QoL and wore an accelerometer to measure sedentary behavior and physical activity between August 2011 and May 2013. RESULTS: Participants (n = 134) averaged 509.7 min/day in sedentary time with 285.2 min/day in short bouts (<20 min) and 224.5 min/day long bouts (≥20 min). Linear regression models indicated that greater total sedentary time was significantly associated with worse physical QoL (b = -0.70, p = 0.02) but not mental QoL (p = 0.92). Models that examined the accumulation of sedentary time in short bouts and long bouts together showed that time in long sedentary bouts was significantly related to physical QoL (b = -0.72, p = 0.02), while time in short bouts was not (p = 0.63). Moderate-to-vigorous intensity physical activity (MVPA) was a significant effect modifier of the relation between time spent in long sedentary bouts and physical QoL (p = 0.028) such that greater time in long bouts was associated with worse physical QoL only among women with lower levels of MVPA. CONCLUSIONS: Findings indicate that time spent in long sedentary bouts is associated with worse physical QoL among breast cancer survivors who do not engage in high levels of MVPA. Future research should examine reducing sedentary time as a potential strategy to improve physical QoL.