Physical activity, risk of death and recurrence in breast cancer survivors: A systematic review and meta-analysis of epidemiological studies

PubMed, EMBASE, and CENTRAL databases were searched up to 18 October 2014. Reference lists of retrieved articles and relevant previous reviews were also searched. Observational studies that reported risk estimates for all-cause and/or breast cancer-related death and/or breast cancer recurrences by levels of physical activity, were included in the review. Random effects models were used to calculate pooled hazard ratios (HR) and 95% confidence intervals (CI) and to incorporate variation between studies. The Newcastle-Ottawa scale was used to critically appraise the risk of bias across studies.

Twenty-two prospective cohort studies were eligible in this meta-analysis. During average follow-up periods ranging from 4.3 to 12.7 years there were 123 574 participants, 6898 all-cause deaths and 5462 breast cancer outcomes (i.e. breast cancer-related deaths or recurrences). The average Newcastle-Ottawa score was six stars (range 4-8). Compared to those who reported low/no lifetime recreational pre-diagnosis physical activity, participants who reported high lifetime recreational pre-diagnosis physical activity levels had a significantly lower risk of all-cause (HR = 0.82, 95% CI 0.70-0.96, p