Purpose: Although evidence is building on the positive effects of physical activity for prostate cancer survivors, less is known about the possible independent effects of sedentary behavior on quality of life and psychological well-being in this population. We determined the extent to which objectively measured moderate-to-vigorous physical activity (MVPA) and sedentary behavior were independently associated with quality of life, anxiety, and depressive symptoms in prostate cancer survivors. Methods: An exploratory cross-sectional analysis was undertaken on baseline data from a multicenter, cluster randomized controlled trial on the efficacy of a clinician referral and 12-week exercise program for men who had completed active treatment for prostate cancer. Multiple regression analyses were performed using data from 98 prostate cancer survivors who wore hip-mounted accelerometers (time spent sedentary defined as < 100 counts per minute [CPM]; MVPA defined as >1,951 CPM) and completed self-report instruments on their quality of life, anxiety, and depressive symptoms. Results were compared with minimal clinically important differences for the quality of life scales. Results: Independent of sedentary behavior, increases in MVPA of between 15 and 33 min/day were associated with clinically important (but not statistically significant) improvements in three quality of life scales (insomnia, diarrhea, and financial difficulties). Independent of MVPA, decreases in sedentary behavior of 119 and 107 min/day were associated with clinically important (but not statistically significant) improvements in physical functioning and role functioning, respectively. Conclusion: Within our exploratory study, modest increases in MVPA and more substantive decreases in sedentary behavior were independently associated with clinically important improvements in several quality of life scales. Further research, including prospective studies, is required to understand sedentary behavior across larger and more representative samples (in terms of their physical, psychological, and social functioning and their engagement in physical activity) of prostate cancer survivors. Trial registration: Australia and New Zealand Clinical Trials Register (ANZCTR): ACTRN12610000609055 .
Cancer Causes and Control / Vol. 27, No. 9, pp.1093-1103