Women who start smoking early in life are at increased risk of breast cancer, a new study concludes.
Previous studies on smoking and breast cancer have produced conflicting results, HealthDay reports. A 2004 report by the U.S. Surgeon General found no cause-and-effect relationship between smoking and the risk of breast cancer.
The new study included data from more than 73,000 women. Over the course of almost 14 years, more than 3,700 women developed invasive breast cancer. The incidence of breast cancer was 24 percent higher in current smokers, and 13 percent higher in women who had quit smoking, compared with women who never smoked.
Women who started smoking before their first menstrual period were 61 percent more likely to develop breast cancer than nonsmokers. Women who started smoking after their first period, but 11 or more years before giving birth, were 45 percent more likely to develop the disease than their nonsmoking peers.
The researchers concluded smoking’s effect on breast cancer risk was independent of alcohol’s effect. Lead researcher Mia Gaudet told HealthDay breast tissue may be more susceptible to toxic exposures before a woman gives birth the first time.
The findings appear in the Journal of the National Cancer Institute.