Physical and psychological health among breast cancer survivors: interactions with sedentary behavior and physical activity.

BACKGROUND: Reducing sedentary behavior (SED) may be one promising strategy to reduce treatment-related side effects in breast cancer given the unique health benefits distinct from the beneficial effects of moderate-to-vigorous intensity physical activity (MVPA).
OBJECTIVES: To examine the associations between SED and the late-effects symptoms of pain, fatigue, and depression among breast cancer survivors (BCS), and the interactive associations between SED, light PA, and MVPA on these symptoms.
METHODS: One hundred and ninety-five BCS provided baseline data 3 to 4 months post-systemic treatment, as part of the Life After Breast Cancer: Moving On longitudinal study. Pain, fatigue, and depression symptoms were assessed using validated self-report questionnaires. Objective measures of MVPA, light PA, and SED (i.e. sitting time) were assessed by accelerometers over the same period. Self-reported demographic and medical variables were collected.
RESULTS: In hierarchical multiple regression analyses, the interaction effect of MVPA by SED was significantly associated with pain (p = .02), fatigue (p = .01), and depression (p = .006). Follow-up simple slope analyses demonstrated that among BCS with lower levels of MVPA, higher levels of SED significantly predicted higher levels of fatigue (p < .001), higher levels of pain (p = .06), and higher levels of depression (p = .08).
CONCLUSIONS: SED was associated with higher levels of fatigue, pain, and depression in BCS, and was more pronounced among those with lower levels of MVPA. However, SED was not associated with these symptoms among BCS with higher levels of MVPA. Pairing health promotion messages to reduce SED and increase MVPA are likely to result in better symptom management.