Physical activity and survival following breast cancer.

ABSTRACT

INTRODUCTION: Physical activity (PA) leads to improved survival in women following the diagnosis of breast cancer, but it is less clear whether PA has equally positive effects regardless of age at diagnosis. The purpose of our study was to evaluate the association between post-diagnosis PA and survival in women aged below or over 55 years at diagnosis. METHODS: From a prospective population-based cohort of Swedish women, we included 847 women, aged 34-84 years, who were diagnosed with breast cancer from 1992 to 2012. A PA score was calculated based on three different questions regarding self-reported PA. Cox proportional hazard model was used to estimate the association between PA and mortality. RESULTS: A significant association between PA score and all-cause mortality was observed, in a dose-response manner (ptrend  = 0.01). The mortality was clearly lower in the most active compared to the least active group (hazard ratio 0.29, 95% confidence intervals 0.09-0.90). A subgroup analysis showed that the improved survival was only seen in women over 55 years of age at diagnosis. CONCLUSION: Physical activity, which is a modifiable lifestyle factor, should be encouraged after breast cancer diagnosis, especially in women with post-menopausal breast cancer.