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Author: Stephanie McClain Riddle PharmD, July 5 2014

The number one risk factor for the development of breast cancer, aside from being female, is advancing age. According to a review of the literature from the National Cancer Institute, the short-term risk for the development of breast cancer is about 10 times greater in a 70 year old woman than that of a woman 30 years of age.

Additional risk factors identified by the National Cancer Institute, such as genetics and breast density, are discussed here, as well as modifiable factors and lifestyle considerations that may aid in reducing the risk of developing breast cancer.

Some factors that increase the risk of breast cancer include early menarche, or having the first menstrual period at an early age, late onset of menopause, regular alcohol consumption of 4 drinks or more each day, and nulliparity. Nulliparity means never having born a child or carried a pregnancy into at least its 20th week. In some women, taking a combination estrogen-progesterone hormone after menopause, may also increase the risk.

Exposure to ionizing radiation in the chest area during the age of puberty and young adulthood is a risk factor, as is women with an inheritable gene mutation, often evidenced by a family history of breast cancer, especially in a first degree relative such as a sister or mother. Breast density has also been shown to be a risk factor. Compared to women with the lowest breast density, women with dense breasts have an increased risk, ranging from about a 1.79 times greater risk with slight density to a 4.64 times greater risk in women with very dense breasts.

Obesity has been associated with an increased incidence of breast cancer cases according to data collected in The Women’s Health Initiative Study. Postmenopausal women weighing 180 pounds or more were found to have a 2.85 times greater risk than postmenopausal women weighing about 129 pounds. It is unclear if postmenopausal weight reduction significantly alters the odds.

A decrease in the risk of breast cancer development has been associated with factors such as early pregnancy, breast feeding, and exercise. Women who gave birth before 20 years of age have a 50% decreased risk compared to women giving birth after age 35 and nulliparous women. Breast feeding decreases the odds of developing breast cancer at an overall rate of 4.3% for every 12 months of breast feeding. Exercise regimens including strenuous activity for more than 4 hours each week are associated with a 30% to 40% reduction in breast cancer risk, especially in women of normal or low body weight.

The National Cancer Institute provides detailed information about breast cancer including risks in specific patient populations. Visit their website at for more information. Self-exam, regular mammography, and routine physician visits are recommended. Contact your physician if you notice any changes or if you have any questions. Early diagnosis is critical to effective treatment.

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