Increasing age - The risk for breast cancer increases with age; most breast cancers are diagnosed after age 50.
Genetic mutations - Approximately 5% to 10% of breast cancers are thought to be hereditary, caused by abnormal genes passed from parent to child.
Menstrual history - Women who start their periods before age 12 are exposed to hormones longer, raising the risk for breast cancer.
Late or no pregnancy - Having the first pregnancy after age 30 and never having a full-term pregnancy can raise breast cancer risk.
Starting menopause after age 55 - Being exposed to oestrogen hormones for a longer time later in life raises the risk of breast cancer.
Sedentary lifestyle - Women who are not physically active have a higher risk of getting breast cancer.
Overweight and obesity - Women who are overweight or obese have a higher risk of getting breast cancer than those at a normal weight, this is especially true for women post-menopause.
Having dense breasts - Dense breasts have more connective tissue than fatty tissue, which can sometimes make it hard to see tumours on a mammogram.
Combination hormone therapy - Taking hormones to replace missing oestrogen and progesterone in menopause for more than five years raises the risk for breast cancer.
Oral contraceptives - Certain forms of oral contraceptive pills have been found to raise breast cancer risk.
History of breast cancer - Women who have had breast cancer are more likely to get breast cancer a second time.
Family history of breast cancer - A woman’s risk for breast cancer is higher if she has a mother, sister, or daughter (first-degree relative) or multiple family members on either her mother’s or father’s side of the family who have had breast cancer.
Radiation therapy - Women who had radiation therapy to the chest or before age 30 have a higher risk of getting breast cancer later in life.
Alcohol consumption - Research consistently shows that drinking alcoholic beverages increases a woman's risk of breast cancer.
Race/Ethnicity - White women are slightly more likely to develop breast cancer than Black, Hispanic, and Asian women. But Black women are more likely to develop more aggressive, more advanced-stage breast cancer that is diagnosed at a young age.