Higher cardiorespiratory fitness may be protective against breast cancer in postmenopausal women

1. In this prospective cohort study, higher cardiorespiratory fitness (CRF) was associated with a substantially lower risk of breast cancer in postmenopausal women.

2. However, this protective effect of high CRF was only seen in those with overweight/obesity or a higher body fat percentage.

Evidence Rating Level: 2 (Good)

Several risk factors exist for developing breast cancer, especially in postmenopausal women. Cardiorespiratory fitness (CRF) represents a modifiable risk factor that may affect the risk of developing breast cancer. The evidence for CRF to reduce the incidence of breast cancer has not been well established. As a result, the objective of the present prospective study was to evaluate the association between CRF and invasive breast cancer in postmenopausal women.

The present study recruited 17,840 (median age= 60 years) cancer-free postmenopausal women who had a CRF assessment from the UK Biobank between 2006 and 2010. Participants were included if they had not had a menstrual period for >365 days, had a history of double oophorectomy, or had no other menstrual information available but were older than 55 years. Women were excluded if they had a personal history of cancer or mastectomy at baseline. Estimated CRF (eCRF) was assessed using a submaximal bicycle test and was classified as low (<20th percentile), moderate (20th to <80th percentile), and high (≥ 80th percentile). Statistical analyses were performed using regression models. The primary outcome was the time from baseline assessment to incident breast cancer diagnosis.

The results demonstrated that over a median follow-up of 11 years, 3% of women were diagnosed with invasive breast cancer. Patients with higher eCRF had a 24% lower risk of developing breast cancer than those with a low or moderate eCRF. However, it was found that this result was limited to those who were classified as having overweight/obesity. The study was limited by using a submaximal bicycle test to determine eCRF, rather than the gold standard: a maximal treadmill test with oxygen expiration capture. However, these results suggested that in certain populations, eCRF may decrease the incidence of breast cancer among postmenopausal women.

Click to read the study in British Journal of Sports Medicine

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