Because more women are living longer, it's not surprising that more women are at risk of breast cancer. But there are other factors in addition to age at work as well.
Family history of the disease is a significant and unfortunately unmodifiable risk factor. Thus, a woman is at a much higher risk if her mother or a sister has had breast cancer, and she'll want to be very careful to change other risk factors that can be modified.
Alcohol consumption may also increase the risk. A high-fat diet is thought to be a factor, though Willet Walter's study with nurses says otherwise. Women in countries such as Japan, where they consume much less dietary fat, have a significantly lower risk of breast cancer than American women. Japanese women who move to this country and who, over time, adopt more American-style eating and other habits eventually come to have the same risk as other American women.
Being overweight is also associated with an increased risk of breast cancer, particularly in the menopausal years. Because obesity can be a result of both diet and activity patterns, dietary changes to reduce fats will also likely reduce calories consumed.