What are some lifestyle-related factors that increase breast cancer risk?

Not having children, or having them later in life

Women who have had no children or who had their first child after age 30 have a slightly higher breast cancer risk. Having many pregnancies and becoming pregnant at a young age reduce breast cancer risk. Pregnancy reduces a woman's total number of lifetime menstrual cycles, which may be the reason for this effect.

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. This risk seems to decline back to normal over time once the pills are stopped. Women who stopped using oral contraceptives more than 10 years ago do not appear to have any increased breast cancer risk. When thinking about using oral contraceptives, women should discuss their other risk factors for breast cancer with their health care team.

Not breast-feeding

Some studies suggest that breast-feeding may slightly lower breast cancer risk, especially if breast-feeding is continued for 1½ to 2 years. But this has been a difficult area to study, especially in countries such as the United States, where breast-feeding for this long is uncommon.

The explanation for this possible effect may be that breast-feeding reduces a woman's total number of lifetime menstrual cycles (similar to starting menstrual periods at a later age or going through early menopause).

Alcohol

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 1 alcoholic drink a day have a very small increase in risk. Those who have 2 to 5 drinks daily have about 1½ times the risk of women who drink no alcohol. Excessive alcohol use is also known to increase the risk of developing cancers of the mouth, throat, esophagus, and liver. The American Cancer Society recommends that women limit their consumption of alcohol to no more than one drink a day.

Certain factors may increase the risk of having breast cancer.  Normally, this is associated with increased estrogen levels at an earlier age.  Women who use oral contraceptives with estrogen have been seen to have a slight increase risk for breast cancer.  Women who are nulliparous, or have had no children, also have a higher risk of breast cancer due to increased estrogen levels.  Those who have not breastfed may have an increased slight risk as well.  Finally, use of alcohol has been linked to the risk of development of breast cancer.  Women should consume less than 1 drink a day.  Those who drink over two to five will increase the risk significantly.