Risk factors for breast cancer

Risk factors for breast cancer may be divided into preventable and non-preventable. Their study belongs in the field of epidemiology. Breast cancer, like other forms of cancer, can result from multiple environmental and hereditary risk factors. The term environmental, as used by cancer researchers, means any risk factor that is not genetically inherited.

For breast cancer, the list of environmental risk factors includes the individual person's development, exposure to microbes, "medical interventions, dietary exposures to nutrients, energy and toxicants, ionizing radiation, and chemicals from industrial and agricultural processes and from consumer products...reproductive choices, energy balance, adult weight gain, body fatness, voluntary and involuntary physical activity, medical care, exposure to tobacco smoke and alcohol, and occupational exposures, including shift work" as well as "metabolic and physiologic processes that modify the body's internal environment."^[1] Some of these environmental factors are part of the physical environment, while others (such as diet and number of pregnancies) are primarily part of the social, cultural, or economic environment.^[1]

Although many epidemiological risk factors have been identified, the cause of any individual breast cancer is most often unknowable. Epidemiological research informs the patterns of breast cancer incidence across certain populations, but not in a given individual. Approximately 5% of new breast cancers are attributable to hereditary syndromes, and well-established risk factors accounts for approximately 30% of cases.^[2] A 2024 review found that there is a convincing association between increased breast cancer risk with high BMI and weight gain in postmenopausal women and a decreased risk from high fiber intake and high sex hormone-binding globulin levels.^[3]