Age is a well-established risk factor for breast cancer. The older a woman is, the more likely she is to get breast cancer. Rates of breast cancer are low in women under age 40. Rates 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 are age 40 or older [4].
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). To learn more, see Male Breast Cancer.
Why does age increase the risk of breast cancer? As we get older, it becomes more likely that abnormal changes will take place in our cells. When many of these types of changes occur within the cells, cancer can develop.
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 years 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 appear on the scale used in this graph.
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Updated 11/09/09
