Doctors have long suspected some type of link between cigarette smoking and breast cancer risk, but research results have been mixed. A very large study found that women who started smoking heavily at an early age and smoked for a long time had a 25% higher risk of breast cancer.
The Nurses' Health Study is a large, ongoing study that's been following the health of more than 100,000 nurses who were healthy when the study started. Every other year participating nurses fill out a survey about their health, diet, and lifestyle habits such as smoking and alcohol use, vitamin use, and how much and how hard they exercise. One goal of the study is to identify links between diet and lifestyle factors and health problems such as cancer.
In the study, the researchers looked at the health information of 111,140 women in the Nurses' Health Study from 1976 to 2006. None of the women had been diagnosed with breast cancer when they joined the study. Over the 30 years, 8,772 cases of breast cancer were diagnosed. The researchers compared the smoking histories of women who were diagnosed to women who weren't diagnosed.
Overall, ANY history of smoking (once long ago or heavy smoking for 35 years or more) was linked to a slight (6%) increase in breast cancer risk. While this overall increase in risk was small, the study found that the earlier a woman started smoking and the longer she smoked, the greater her risk of being diagnosed with breast cancer.
Breast cancer risk increased the most -- 25% -- in women who:
- started smoking younger than 18
- smoked for more than 35 years
- smoked an average of more than 25 cigarettes per day
Regularly being around people who smoke (passive smoking) didn't increase breast cancer risk in women who didn't smoke, but did in women who smoked.
Smoking can harm your health, including breast health, at any age. If you don't smoke, don't start. If you do smoke, find a program or system to help you quit. Quitting is tough, but it's definitely worth it. The American Lung Association offers a free online smoking cessation program. Local chapters of the American Cancer Society offer the Fresh Start program to help people quit smoking. You can also call the ACS "Quitline" at 1-800-ACS-2345 to get support and free advice on how to stop smoking from trained counselors.