Significantly greater reduction in breast cancer mortality from post‐diagnosis running than walking

Abstract

The purpose of these analyses is to test prospectively whether post-diagnosis running and walking differ significantly in their association with breast cancer mortality. Cox proportional hazard analyses were used to compare breast cancer mortality to baseline exercise energy expenditure (METs, 1 MET-hour ffi1 km run) in 272 runners and 714 walkers previously diagnosed with breast cancer from the National Runners' and Walkers' Health Studies when adjusted for age, race, menopause, family history, breastfeeding and oral contraceptive use. Diagnosis occurred (mean 6 SD) 7.9 6 7.3 years before baseline. Forty-six women (13 runners and 33 walkers) died from breast cancer during 9.1-year mortality surveillance. For the 986 runners and walkers combined, breast cancer mortality decreased an average of 23.9% MET-hours/day [95% confidence interval (CI): 7.9-38.3%; p 5 0.004]. There was a significantly greater decrease in risk for running than walking (risk per MET-hours/day run vs. walked: p 5 0.03). For the 272 runners analyzed separately, breast cancer mortality decreased an average of 40.9% per METhours/day run (95% CI: 19.3-60.0%, p 5 0.0004). When analyzed by categories of running energy expenditure, breast cancer mortality was 87.4% lower for the 1.8-3.6 MET-hours/day category (95% CI: 41.3-98.2% lower, p 5 0.008) and 95.4% lower for the !3.6 MET-hours/day category (95% CI: 71.9-100% lower, p 5 0.0004) compared to the <1.07 MET-hours/day category. In contrast, the 714 walkers showed a nonsignificant 4.6% decrease in breast cancer mortality per MET-hours/day walked (95% CI: 27.3% decreased risk to 21.3% increased risk, p 5 0.71). These results suggest that post-diagnosis running is associated with significantly lower breast cancer mortality than post-diagnosis walking.An estimated 23% of women diagnosed with invasive breast cancer die within 15 years of diagnosis. 1 Physical activity may improve survival in women diagnosed with breast cancer, but the evidence is mixed, with some studies showing physical activity significantly reduces their breast cancer mortality 2-7 and others showing no significant reduction. [8][9][10][11][12] Meta-analyses that combine study results provide stronger evidence for improved survival. For example, meeting the current physical activity recommendations has been associated with a 25% reduction in breast cancer mortality in 13,302 breast cancer survivors of the After Breast Cancer Pooling Project. 13 Other meta-analyses found 29% (including lifetime and at diagnosis physical activity) 14 and 34% reductions 15 in breast cancer mortality with post-diagnosis physical activity when various study results were combined.This report tests whether post-diagnosis running and walking produce equivalent reductions in breast cancer mortality. Running and walking differ by exercise intensity. Running is classified as vigorous because it expends !6 times the energy expenditure of sitting at rest (!6 metabolic equivalents or METs, 1 MET 5 3.5 mL O 2 /kg/min), whereas walking is classified as moderate be...

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