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An hour of daily physical activity reduces the risk of breast cancer, regardless of age or weight, according to the results of a study presented at the 2014 European Breast Cancer Conference in Glasgow, Scotland.

Each year, roughly 227,000 women are diagnosed with breast cancer and close to 40,000 die of the disease.

Regular physical activity has been shown to improve overall health and wellbeing as well as reduce the risk of cancer. Some studies have shown that physical activity is associated with a reduced risk of breast cancer. In contrast, hormone replacement therapy appears to increase the risk. To evaluate the impact of physical activity on breast cancer risk—and whether hormone replacement therapy influenced this impact—researchers conducted a meta-analysis of 37 studies published between 1987 and 2013. In total, the studies included data from over 4.2 million women.

After comparing the women with the highest level of physical activity to those with the lowest level of physical activity, the researchers found that those with the highest level of physical activity reduced their risk of breast cancer by 12 percent. This benefit was seen regardless of age, weight, or geographic location. In fact, the age at beginning physical activity appeared to have no bearing on the results.

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One key finding, however, was that any benefits provided by physical activity appeared to be cancelled out among women who were taking hormone replacement therapy. What’s more, women with estrogen receptor-negative breast cancer appeared to reap more benefits from physical activity than those with hormone receptor-positive cancer.

The researchers concluded that women who get an hour or more of physical activity per day have a reduced risk of breast cancer, unless they are taking hormone replacement therapy. The reasons for the risk reduction are unclear because the results are independent of body mass index, suggesting that factors beyond weight control are involved.


Autier P, Pizot C, Boniol M, et al: Physical activity, hormone replacement therapy and breast cancer risk: A meta-analysis of prospective cohort studies. Presented at the 2014 European Breast Cancer Conference in Glasgow, Scotland. Abstract 111.

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