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Smoking and Secondhand Smoke Raise Risk

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Doctors have long suspected a link between smoking and breast cancer risk, but research results have been mixed. A study combined and analyzed the results of many earlier studies and found that both smoking and exposure to secondhand smoke do raise breast cancer risk. Looking at the results from many different studies all looking at the same issue is called a meta-analysis.

The study found that breast cancer risk is higher in:

  • premenopausal women who smoke -- women who start smoking at an early age are 20% more likely to develop breast cancer than women who never smoke
  • postmenopausal women who smoke
  • premenopausal women exposed to secondhand smoke

Postmenopausal women exposed to secondhand smoke didn't have an increase breast cancer risk in this study.

This study doesn't say how smoking increases breast cancer risk. We do know that cigarette smoke contains compounds called aromatic amines. Certain aromatic amines are known to cause cancer.

The study also confirmed a link between a gene and how much smoking affects breast cancer risk. Smoking and secondhand smoke exposure raises breast cancer risk more in women who have a slow-acting form of the NAT2 gene. The slow-acting NAT2 gene slows the body's ability to get rid of aromatic amines. Breast cancer risk in all long-term smokers is about 20% higher than in non-smokers. This study found that breast cancer risk was 27% higher in women with the slow-acting NAT2 gene who smoked. Other research has found that risk is 35% to 50% higher in long-term smokers with the slow-acting NAT2 gene.

About 50% to 60% of white women and 35% to 40% of Black women have the slow-acting NAT2 gene. Some research has suggested that women who smoke and don't have the slow-acting NAT2 gene don't have a higher risk of breast cancer. Still, smoking can harm your heart and lungs affect your overall health. A routine test for the slow-acting NAT2 gene isn't available, so women usually don't know if they have it.

Smoking can harm your health, including your 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.

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