Smoking, breast cancer: jury still out.

Smoking, breast cancer: Jury still out

A growing body of evidence indicates that women who smoke cigarettes have lower estrogen levels than those who don't--a hormonal reduction that would appear to help protect premenopausal women against estrogen-dependent breast cancers. Researchers have also noted that women smokers typically begin menopause about one year earlier than non-smokers, and other studies have linked earlier onset of menopause with a reduced risk of breast cancer, says CDC epidemiologist Nancy E. Stroup. But new research showing a slight increase in breast cancer risk among cigarette smokers sheds doubt on smoking's "protective effect."

In the retrospective study, Stroup and her colleagues collected data on 4,720 women diagnosed with breast cancer between the ages of 20 and 54, and compared them with 4,682 controls in the same age range who had no history of breast cancer. The data, described in the February AMERICAN JOURNAL OF EPIDEMIOLOGY, show that the women who reported having smoked more than 100 cigarettes in their lives faced a breast cancer risk 1.2 times that of those who never smoked. The risk of breast cancer did not consistently increase with the number of cigarettes a women smoked each day or the number of years she smoked. Stroup speculates that cigarette smoking has unidentified effects that enhance breast cancer risk, counter-balancing the beneficial effect of lowered estrogen.