Physical activity and breast cancer risk: results from the UK Biobank prospective cohort

Abstract

BACKGROUND: Previous studies suggest a protective role of physical activity in breast cancer risk, largely based on self-reported activity. We aimed to clarify this association by examining breast cancer risk in relation to self-reported physical activity, informed by accelerometer-based measures in a large subset of participants. METHODS: We analysed data from 47,456 premenopausal and 126,704 postmenopausal women in UK Biobank followed from 2006 to 2014. Physical activity was self-reported at baseline, and at resurvey in a subsample of 6443 participants. Accelerometer data, measured from 2013 to 2015, were available in 20,785 women. Relative risks (RRs) and 95% confidence intervals (CIs) were calculated by using multivariable-adjusted Cox regression. RESULTS: A total of 3189 cases were diagnosed during follow-up (mean = 5.7 years). Women in the top compared with the bottom quartile of self-reported physical activity had a reduced risk of both premenopausal (RR 0.75; 95% CI 0.60-0.93) and postmenopausal breast cancer (RR 0.87; 95% CI 0.78-0.98), after adjusting for adiposity. In analyses utilising physical activity values assigned from accelerometer measurements, an increase of 5 milli-gravity was associated with a 21% (RR 0.79; 95% CI 0.66-0.95) reduction in premenopausal and a 16% (RR 0.84; 95% CI 0.73-0.96) reduction in postmenopausal breast cancer risk. CONCLUSIONS: Greater physical activity is associated with a reduction in breast cancer risk, which appears to be independent of any association it may have on risk through its effects on adiposity.

A systematic review of the biological mechanisms linking physical activity and breast cancer

“…In recent years, epidemiological studies have been conducted on the relationship between physical activity and cancer outcomes, demonstrating a protective role of physical activity in breast cancer [ 4 - 8 ]. Leisure-time physical activity is associated with lower risks of 13 types of cancer [ 5 ], and exercise-associated reduction in breast cancer risk has been apparent in early-stage breast cancer patients [ 6 ].…”

Body size and composition, physical activity and sedentary time in relation to endogenous hormones in premenopausal and postmenopausal women: Findings from the UK Biobank

“…4 In contrast, physical activity, one of the most modifiable lifestyle factors, appears to reduce the risk of several cancers, possibly independently of adiposity. [5][6][7] The associations between obesity, physical activity and cancer risk may be explained by a number of biological mechanisms including changes in hormones, metabolism, immune function and inflammation. 8 Endogenous hormones play an important role in carcinogenesis by promoting cell proliferation and therefore increasing the chances of random genetic errors.…”

Personalized early detection and prevention of breast cancer: ENVISION consensus statement

“…Notably, the efficacy of weight loss programmes has been shown to be greater among individuals who are aware of being at high risk of developing breast cancer 143 . Importantly, weight loss 144 and regular exercise 145,146 not only decrease breast cancer risk but also the risks of other cancers and CVDs. Considering the general health benefits, lifestyle interventions could be recommended to women at all levels of breast cancer risk 147 .…”