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Exercise linked to lower risk of early breast cancer

By Julie Bierach, KWMU

SAINT LOUIS, MO – A study conducted by researchers at Washington University and Harvard University has found that regular exercise between the ages of 12 and 35 reduces a woman's risk of early breast cancer.

In particular, scientists found that high levels of physical activity between the ages of 12 and 22 contributed most strongly to a lower breast cancer risk before menopause.

In the study, researchers followed 65,000 female nurses ages 24 to 42. Every year, the women filled out detailed questionnaires about their level of exercise from the age of 12 and on. After 6 years, 550 women had been diagnosed with breast cancer.

Lead investigator Dr. Graham Colditz says they found that those who were physically active had a 23% lower risk of early breast cancer.

"Best explanation at this stage comes down to higher activity levels being related to lower circulating hormone levels," said Dr. Colditz who is also the Niess-Gain Professor and associate director of Prevention and Control at the Siteman Cancer Center at Washington University School of Medicine and Barnes-Jewish Hospital.

Young women who exercise reduce the level of estrogen in the body. Previous studies have shown that the more a woman is exposed to estrogen, the greater her risk of developing breast cancer.

"Preventing a quarter of the cases of breast cancer happens when we get to the level of half an hour of vigorous activity or running per day, or two hours of walking per day," said Colditz.

The study appears in the Journal of the National Cancer Institute and is the largest and most detailed analysis to date of the effects of exercise on premenopausal breast cancer.

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