• Walking, cycling cuts breast cancer risk – study


    For women past childbearing age, a new study finds that a modest amount of exercise —four hours a week of walking or more intensive physical activity such as cycling for just two hours a week—drives down breast cancer risk by roughly 10 percent.

    If exercise were a pill, its effectiveness in driving down a woman’s breast cancer risk would occur fairly quickly, the new research says: When women reported at least this modest level of physical activity over the last four years, they were less likely to have developed malignancy in a breast.

    But, like a pill, exercise must be continued for the effect to endure: Even if a woman had been physically active earlier in life, when her reported physical activity levels dropped below the equivalent of four hours of weekly walking, her risk of developing breast cancer went back up.

    At the same time, the research found that engaging in more physical activity than 12 “metabolic equivalents” per week—either via greater intensity or longer duration of exercise—did not further drive down a woman’s likelihood of breast cancer. The authors suggested that finding such a “dose response” might have required a more detailed record of participants’ energy expenditures than was collected by the European researchers who designed the study.

    The new findings were culled from the French component of the European Prospective Investigation Into Cancer and Nutrition. In all, 59,308 French women ages 43 to 78—most of them teachers—started answering detailed surveys about their health and health behaviors in 1993 and did so every four years until 2005.

    The researchers sought to clarify the role of physical activity in reducing breast cancer risk in postmenopausal women, a stage of life in which the probability of a woman developing breast cancer rises steadily.

    The designers of the study used a very rough measure of physical activity: They asked women to quantify the average time they spent walking (including walking to work or shopping), cycling or engaging in sports during a typical two-week period in the winter and in the summer. They assigned walking a “metabolic equivalent task” value of three per hour, and cycling and sports a “MET” value of six.



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