Exercise Combats Postmenopausal Breast Cancer Risk

Women could reduce their risk of postmenopausal invasive breast cancer by walking for a total of just 4 hours per week

medwireNews: Modest amounts of exercise protects women against the development of postmenopausal invasive breast cancer, French researchers have found.

The team studied data from the French E3N [European Prospective Investigation into Cancer and Nutrition] cohort of 59,308 postmenopausal women, the majority of whom are teachers. The women were recruited between 1993 and 2005, during which time 2155 incident invasive breast cancers were detected.

Women who walked, cycled or played sport to a physical activity level of 12 metabolic equivalent task-hours (MET-h) per week in the past 4 years had a 10% lower risk of breast cancer than those with lower levels of physical activity, after adjusting for a raft of characteristics including family history of breast cancer, hormone use, and age at menarche and first full-term pregnancy.

“Twelve MET-h per week corresponds to walking four hours per week or cycling or engaging in other sports two hours per week and it is consistent with the World Cancer Research Fund recommendations of walking at least 30 minutes daily”, said lead author Agnès Fournier, from the Institut Gustave Roussy in Villejuif, France, in a press release.

"So, our study shows that it is not necessary to engage in vigorous or very frequent activities; even walking 30 minutes per day is beneficial."

The risk reduction remained after accounting for additional confounding factors such as education, history of physical activity in childhood, recent mammogram, hormone use and participation in other activities such as gardening.

However, women’s physical activity levels 5 to 9 years earlier did not significantly predict their risk of breast cancer.

“This suggests that starting recreational physical activity may be followed relatively rapidly by a reduction in breast cancer risk in postmenopausal women, a reduction that may disappear a few years after the activity stops”, the researchers write in Cancer Epidemiology, Biomarkers & Prevention.

In addition, the relationship between postmenopausal breast cancer risk and physical activity was not significantly influenced by breast cancer oestrogen or Progesterone receptor status, or by body mass index, waist circumference or recent weight gain.

This suggests a nonhormonal protective mechanism, say Agnès Fournier and team, such as decreased inflammation, immunomodulation, interference with the glycolytic switch or a reduction in DNA damage.

Nevertheless, the authors conclude: “Because the women participating in the cohort are fairly slender teachers, our results should be replicated in populations with different genetic, anthropometric, and occupational characteristics.”

Reference

Fournier A, Dos Santos G, Guillas G, et al. Recent recreational physical activity and breast cancer risk in postmenopausal women in the E3N cohort. Cancer Epidemiol Biomark Prev 2014; Published online first 11 August. doi: 10.1158/1055-9965.EPI-14-0150

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