Other probable risk factors are harder to pinpoint. For example, breast cancer is most common among Caucasians and occurs much less often among Asians. Although black women are less likely to develop breast cancer than white women, black women are more likely to die of the disease. For some reason, breast cancer seems to occur more often among the wealthier and better educated. Some data suggest that alcohol use or a high-fat diet increases risk of breast cancer, but this has not been confirmed.
Smoking does increase the risk of breast cancer for some postmenopausal white women.
Other studies suggest that vigorous exercise at certain ages may reduce the risk. Women who have previously had cancer of one breast are at higher risk of developing it in the other. Women with a certain type of noncancerous lesion in the breast, called a radial scar, are more likely to develop cancer where the scars are found. Because the breast is extremely vulnerable to the effects of radiation, previous exposure to radiation increases the odds of breast cancer, especially for women exposed before the age of 30. Exposure as a young girl is a particular cause for worry.