For most women, breast cancer develops because of a range of risk factors and it is not possible to identify just one thing that caused it.
- Increasing age
As with most cancers, your risk of developing breast cancer increases with your age. Ovarian cancer is uncommon in women younger than 40 and most ovarian cancers develop in women aged 75 to 79, after menopause.
- A high body mass index (BMI) and physical inactivity
Your BMI is calculated using your age, height, and weight. It provides a weight classification based on a scoring system ranging from less than 18.5, 18.5 to 24.9, 25 to 29.9, and 30 to 39.9, i.e. underweight, healthy, overweight, and obese, respectively. An increased BMI is associated with an increased risk for many cancers, including breast and ovarian cancer.
- Family History of Breast and Ovarian Cancer
Having a mother, sister, or daughter who have been diagnosed with breast cancer is associated with an increase in risk, depending on number of affected relatives and their age when they were diagnosed.
- Smoking
Cigarette smoking is associated with an increased risk of breast cancer in older women who are postmenopausal.