Factors that increase the risk of breast cancer

Simply being a woman and getting older puts you at risk for developing breast cancer. The older you are, the greater your chance of getting breast cancer. The breast cancer incidence rate, per 100,000 women per year, is 222 for women age 40 to 64; for women older than 65, it climbs to 435.

Risk is also increased for older women who have a family history of breast cancer. The mothers, daughters, and sisters of women with breast cancer, especially if the relative developed this cancer at a young age, are two to five times more likely to develop breast cancer themselves than are women without a family history. Women who themselves have already had cancer in one breast also run an increased risk of developing cancer in the other breast.

To a lesser extent, risk is influenced by various aspects of a woman's reproductive history. Risk is increased for women who began menstruating earlier (before age 12, compared to after 15), had their first child later (after age 30, compared to before 20) or were never pregnant, or completed menopause later (after age 55 compared to women who had their ovaries removed-a "surgical menopause"-at age 45).

Risk is also increased for women who are overweight, especially those who carry excess fat in the upper body-abdomen, shoulders, nape of the neck. As noted above, risk is increased moderately for women who have the benign breast changes known as atypical hyperplasia.

Many aspects of the American lifestyle are suspected of possibly influencing the growing incidence of breast cancer. Current research is looking into the roles of obesity, hormones, and fat metabolism; the risks and benefits of postmenopausal hormone replacement therapy; the impact of taking oral contraceptives at an early age and for many years; alcohol use; and diet. Caffeine, on the other hand, appears to have no influence on the incidence of breast cancer.

It is important to keep in mind that these factors that increase cancer risk- risk factors -do not necessarily cause cancer; they are merely associations. Having one or more does not mean that you are certain or even likely to develop breast cancer. Even among women with a strong family history-both a mother and a sister or two sisters, one of whom developed breast cancer in both breasts or before menopause-three-fourths will not develop breast cancer.