The risk of breast cancer increases by approximately 10% for each 10 g of daily alcohol intake (approximately one drink or less) in the general population.[47,48] Prior studies of BRCA1/BRCA2 mutation carriers have found no increased risk associated with alcohol consumption.[49,50]
Physical activity and anthropometry
Weight gain and being overweight are commonly recognized risk factors for breast cancer. In general, overweight women are most commonly observed to be at increased risk of postmenopausal breast cancer and at reduced risk of premenopausal breast cancer. Sedentary lifestyle may also be a risk factor. These factors have not been systematically evaluated in women with a positive family history of breast cancer or in carriers of cancer-predisposing mutations, but one study suggested a reduced risk of cancer associated with exercise among BRCA1 and BRCA2 mutation carriers.
Benign breast disease and mammographic density
Benign breast disease (BBD) is a risk factor for breast cancer, independent of the effects of other major risk factors for breast cancer (age, age at menarche, age at first live birth, and family history of breast cancer). There may also be an association between BBD and family history of breast cancer.
An increased risk of breast cancer has also been demonstrated for women who have increased density of breast tissue as assessed by mammogram,[53,55,56] and breast density is likely to have a genetic component in its etiology.[57,58,59]
Other risk factors, including those that are only weakly associated with breast cancer and those that have been inconsistently associated with the disease in epidemiologic studies (e.g., cigarette smoking), may be important in women who are in specific genotypically defined subgroups. For example, some studies have suggested that certain N-acetyl transferase alleles may influence female smokers' risk of developing breast cancer. One study  found a reduced risk of breast cancer among BRCA1/BRCA2 mutation carriers who smoked, but an expanded follow-up study failed to find an association.
Other Risk Factors for Ovarian Cancer