Dr. Bray Links

Wednesday, July 1, 2015

The Risks of Control: Assessing the Link Between Birth Control Pills and Breast Cancer

In 1996, the first large scale meta-analysis — a work of research combining results from multiple studies — pooled 54 studies that involved a total of 53,297 women with breast cancer and 100,239 women without breast cancer. It showed that current and recent use of birth control pills (within the past 10 years) increased the relative risk of breast cancer by up to 25%. (Note: The increase in risk reported in all the studies is relative risk, which means that, according to this study, for a 40-year old woman with no family history of breast cancer, the risk of breast cancer increases from 1.5% normally to 1.9% with use of birth control pills.) The relative risk was higher if women started taking the pills at a younger age; however, the duration of use had no effect. Nevertheless, when women had stopped taking the pills for 10 or more years, the risk returned to the same level as the ones who had never taken pills. The study included many women who took the first formulation of birth control pills, which had a very high dose of estrogen.

Yet another meta-analysis including 34 studies carried out by the Mayo Clinic in 2006 showed that use of birth control pills increased the relative risk of breast cancer in pre-menopausal women by 19%, and that the risk is highest if women used the pills before their first full-term pregnancy []. A more recent meta-analysis that included 20 studies from 1996 to 2011 showed similar results where current use of birth control pills increased the relative risk of breast cancer by up to 30% but there was no increased risk with past use (> 10 years since last use) for women between the ages of 40 and 49.



http://sitn.hms.harvard.edu/flash/2014/the-risks-of-control-assessing-the-link-between-birth-control-pills-and-breast-cancer/

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