Effects of reallocating sedentary time with physical activity on quality of life indicators in breast cancer survivors.

<bold>Objectives: </bold>Physical activity is associated with better quality of life (QOL) among breast cancer survivors. However, it is unknown the extent to which time spent sedentary or replacing this time with active behaviors may affect QOL. Our aim was to determine the effect of substituting time between sedentary and active behaviors on QOL indicators in breast cancer survivors.<bold>Methods: </bold>An isotemporal substitution approach was used to examine the associations of reallocating time to sedentary and active behaviors measured by accelerometry with Functional Assessment of Cancer Treatment-Breast (FACT-B; total, physical, social, emotional, functional well-being, and breast cancer-specific concerns) and the Hospital Anxiety and Depression Scale (HADS) scores in a pooled analysis of breast cancer survivors (n = 753; Mage  = 56.9 ± 9.5 y) from two observational studies.<bold>Results: </bold>Reallocating 30 minutes of sedentary time to 30 minutes of moderate-to-vigorous intensity physical activity (MVPA) was associated with improved FACT-B total (B = 3.0; 95% CI, 0.6-4.5), physical well-being (B = 0.8; 95% CI, 0.33-1.2), and functional well-being (B = 0.6; 95% CI, 0.03-1.2) scores. Reallocating 30 minutes of light activity to 30 minutes of MVPA was associated with improved FACT-B total (B = 2.4; 95% CI, 0.3-6.0) and physical well-being (B = 0.72; 95% CI, 0.27-1.2) scores. There was no significant substitution of time effects on HADS scores.<bold>Conclusions: </bold>Substituting sedentary time with MVPA showed the greatest range of effects across QOL indicators. These results can inform intervention development interventions and more comprehensive activity recommendations for breast cancer survivors. [ABSTRACT FROM AUTHOR]