Identifying population-based approaches to lower breast cancer risk.

During the 1970s and 1980s, a number of factors emerged that were associated with the risk of breast cancer. The majority of these were not modifiable factors and, although much had been learned about breast cancer risk, this information could not be easily translated into recommendations to women for lowering their breast cancer risk. These factors were considered in developing the hypothesis that physical activity would be associated with breast cancer risk, with women who participated consistently in exercise activity having lower risk than inactive women. Since the mid-1990 s a large series of case-control studies and cohort studies have confirmed that physical activity is a modifiable risk factor for breast cancer. Further, when physical activity is a persistent lifestyle practice, reductions in risk are quite clear, with vigorous activities possibly more protective against breast cancer than moderate forms of activity. Thus, maintaining a physically active lifestyle, which has broad health benefits, additionally has the potential to lower breast cancer risk.