A risk factor is anything that affects your chance of getting a disease, such as cancer. Different cancers have different risk factors. For example, exposing skin to strong sunlight is a risk factor for skin cancer. Smoking is a risk factor for cancers of the lung, mouth, larynx (voice box), bladder, kidney, and several other organs.

But risk factors don’t tell us everything. Having a risk factor, or even several, does not mean that you will get the disease. Most women who have one or more breast cancer risk factors never develop the disease, while many women with breast cancer have no apparent risk factors (other than being a woman and growing older). Even when a woman with risk factors develops breast cancer, it is hard to know just how much these factors might have contributed.

Some risk factors, like a person’s age or race, can’t be changed. Others are linked to cancer-causing factors in the environment. Still others are related to personal behaviours, such as smoking, drinking, and diet. Some factors influence risk more than others, and your risk for breast cancer can change over time, due to factors such as aging or lifestyle.



Breast cancer occurs nearly 100 times more often in women than in men.

Age

Two out of three women with invasive cancer are diagnosed after age 55.

If your mother, sister, father or child has been diagnosed with breast or ovarian cancer, you have a higher risk of being diagnosed with breast cancer in the future. Your risk increases if your relative was diagnosed before the age of 50.

If you have been diagnosed with breast cancer in one breast, you have an increased risk of being diagnosed with breast cancer in the other breast in the future. Also, your risk increases if abnormal breast cells have been detected before (such as atypical hyperplasia, lobular carcinoma in situ (LCIS) or ductal carcinoma in situ (DCIS)).

Early menstruation (before age 12), late menopause (after 55), having your first child at an older age, or never having given birth can also increase your risk for breast cancer.

Mutations in certain genes, such as BRCA1 and BRCA2, can increase your risk for breast cancer. This is determined through a genetic test, which you may consider taking if you have a family history of breast cancer. Individuals with these gene mutations can pass the gene mutation onto their children.

Having dense breast tissue can increase your risk for breast cancer and make lumps harder to detect. Be sure to ask your physician if you have dense breasts and what the implications of having dense breasts are.

A sedentary lifestyle with little physical activity can increase your risk for breast cancer.

A diet high in saturated fat and lacking fruits and vegetables can increase your risk for breast cancer.

Being overweight or obese can increase your risk for breast cancer. Your risk is increased if you have already gone through menopause.

Having radiation therapy to the chest before the age of 30 can increase your risk for breast cancer.

Taking combined hormone replacement therapy, as prescribed for menopause, can increase your risk for breast cancer and increases the risk that the cancer will be detected at a more advanced stage.

Some studies suggest that breastfeeding may slightly lower breast cancer risk, especially if it is continued for 1½ to 2 years. One explanation for this possible effect may be that breastfeeding reduces a woman’s total number of lifetime menstrual cycles (similar to starting menstrual periods at a later age or going through early menopause).

Smoking causes a number of diseases and is linked to a higher risk of breast cancer in younger, premenopausal women. Research also has shown that there may be link between very heavy second-hand smoke exposure and breast cancer risk in postmenopausal women.

Consumption of alcohol can increase your risk for breast cancer. The more alcohol you consume, the greater the risk.