Age is a well-established risk factor for breast cancer. The older a woman is, the more likely she is to develop the disease. In general, rates of breast cancer are low in women under age 40, begin to increase after age 40 and are highest in women over age 70 (see Figure 2.1 below). In the United States, 95 percent of the women diagnosed with breast cancer each year are age 40 or older [9].
Age increases the risk of breast cancer because as women get older, it becomes more likely that abnormal changes will take place in their cells. Multiple changes have to occur within cells before cancer will develop.
Age is also a risk factor for male breast cancer. However, breast cancer is less common in men than in women (see Figure 2.1 below). For more information on male breast cancer, click here.
Figure 2.1
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Data source: SEER 2001-2005
Note: Though the graph shows a rate of zero in the 0-19 year age group, there are a few cases of breast cancer in this age group each year in the U.S. The numbers are too small, however, to register on the scale used in the graph.
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Updated 08/14/08
