Smoking may increase the risk of the most common type of breast cancer.

Young women who smoke and have been smoking a pack a day for a decade or more have a significantly increased risk of developing the most common type of breast cancer. That is the finding of an analysis published early online in Cancer, a peer-reviewed journal of the American Cancer Society. The study indicates that an increased risk of breast cancer may be another health risk incurred by young women who smoke.

Patients in the study were 20 to 44 years old and were diagnosed from 2004-2010. The study also included 938 cancer-free controls.

The researchers found that young women who were current or recent smokers and had been smoking a pack a day for at least 10 years had a 60 percent increased risk of estrogen receptor positive breast cancer.