Changes in light-, moderate-, and vigorous-intensity physical activity and changes in depressive symptoms in breast cancer survivors: a prospective observational study.

PURPOSE: Despite the recommendations for cancer survivors to engage in either moderate or vigorous physical activity, light-intensity physical activity may also have beneficial effects on mental health. The purpose of this study was to examine the associations between light, moderate, and vigorous physical activity and depressive symptoms in breast cancer survivors over 1 year post-treatment.
METHODS: Participants (N = 201) were a sample of breast cancer survivors who self-reported depressive symptoms and wore an accelerometer for seven consecutive days to measure physical activity, on five occasions every 3 months post-treatment for cancer.
RESULTS: Based on the results of hierarchical linear modeling, relative to others (i.e., between-person effects) and to oneself (i.e., within-person effects), higher levels of light- and moderate-intensity physical activity, but not vigorous-intensity physical activity, were associated with lower scores of depressive symptoms.
CONCLUSIONS: In the first year post-treatment, increases in light- and moderate-intensity physical activity, but not vigorous-intensity physical activity, were associated with lower scores of depressive symptoms in relation to other study participants (i.e., between-person effects) and when participants were compared to their own typical levels of physical activity (i.e., within-person effects). The findings may have implications for physical activity recommendations following treatment for breast cancer as light-intensity physical activity may play a role in mitigating depressive symptoms over the first year.