The risks for breast cancer can be divided into two types – risks you can change and those you can’t. The ones you can change have to do with your lifestyle.
Not having children, or having them later in life
Women who become pregnant for the first time after age 35, have a two-fold to three-fold higher risk of breast cancer compared to women whose first pregnancy occurred before age 25.
Some studies suggest that breast-feeding may slightly lower breast cancer risk, especially if breast-feeding is continued for 18 months to 2 years.
Recent oral contraceptive use
Studies have found that women using oral contraceptives (birth control pills) have a slightly greater risk of breast cancer than women who have never used them.
Using post-menopausal hormone therapy
Long-term use (several years or more) of combined post-menopausal hormone therapy increases the risk of breast cancer and may also increase the chances of dying of breast cancer.
The use of oestrogen alone does not appear to increase the risk of developing breast cancer significantly, if at all. But when used long term (for more than 10 years), oestogen replacement therapy has been found to increase the risk of ovarian and breast cancer in some studies.
The use of alcohol is clearly linked to an increased risk of developing breast cancer. The risk increases with the amount of alcohol consumed. Compared with non-drinkers, women who consume one alcoholic drink a day have a very small increase in risk. Those who have two to five drinks daily have about 1.5 times the risk of women who drink no alcohol.
There is a four- to five-fold greater incidence of breast cancer in Western industrialised countries than in less developed countries. It has been suggested that dietary factors, particularly the fat content, are responsible. Most studies have found that breast cancer is less common in countries where the typical diet is low in total fat, low in polyunsaturated fat, and low in saturated fat.
Being overweight or obese
Being overweight or obese has been found to increase breast cancer risk, especially for women after menopause.
Lack of physical activity
Evidence is growing that physical activity in the form of exercise reduces breast cancer risk. In one study from the Women’s Health Initiative (WHI) as little as 1.25 to 2.5 hours per week of brisk walking reduced a woman’s risk by 18%. Walking 10 hours a week reduced the risk a little more.
Factors with uncertain, controversial, or unproven effect on breast cancer risk
Research is ongoing to determine the effect of antiperspirants, breast implants, smoking and chemicals in the environment on the risk for getting breast cancer.