Here's What That Study Linking Birth Control To Breast Cancer *Actually* Means
If you're on hormonal birth control, you might be concerned by recent headlines warning about a possibility of increased health risks. But here's what that study linking birth control to breast cancer actually means, and why you really shouldn't sweat it. Researchers from the University of Copenhagen analyzed data from 1.8 million women in Denmark between age 15 and 49 for an average of 10.9 years, and found that, compared to women who had never used hormonal birth control, the subjects had an increased rate of breast cancer that appeared to rise concurrent with the length of time they used the pill or IUDs, for both estrogen-progestin and progestin-only formulas.
Women who used hormonal contraceptives for under a year had a 9-percent increase in breast cancer cases, and those who used them for over 10 years saw a 38-percent increase. Those who used them for over five years appeared to have an increased breast cancer risk for at least five years even after they stopped. The overall average increase was 20 percent. That sounds bad, right? But it's actually not! Out of the 1.8 million women, there were 11,517 cases of breast cancer, a rate of just 0.64 percent. Compared to women who had never used hormonal contraceptives, that amounts to just 13 more cases, or about one case per year per 7,690 women.
Obviously, breast cancer is devastating for the one of out 7,690, but there's no reason to go chucking your pills in the trash, or making an OB-GYN appointment to remove your Mirena. According to Harvard Medical School's Dr. Mallika Marshall, who also serves as a medical reporter for Boston's WBZ-TV, "The risk is still very small, so I want to reassure women out there, this does not mean that you need to stop your birth control." Marshall encourages women, particularly those who are already at an increased risk for breast cancer, to talk to their doctors if they're concerned, but "it's not anything that anyone needs to panic about."
Dr. David Hunter, Professor of Epidemiology and Medicine at the University of Oxford, translated the study's findings in an editorial for the New England Journal of Medicine, pointing out that breast cancer incidence is rare in young women, even those on hormonal contraceptives. The study found that women under 35 who took hormonal contraceptives for less than a year only had one extra case of breast cancer per 50,000 compared to those who didn't use hormonal contraceptives. Breast cancer risk naturally increases with age, which accounts for the rising rates; women who have been on hormonal birth control for a decade or more would tend to be older than those who have only used it for a year. And while the short-term risk may be greater even after stopping birth control, there's no significant difference by the time breast cancer rates peak around ages 50 to 70, when you're definitely not on it anymore.
If you're still concerned about the small increased risk of breast cancer, let's talk about the benefits of hormonal contraceptives, and no, I don't just mean the obvious things like avoiding your period, controlling cramps and acne, or that other little thing... What is it again? Oh, right, preventing unplanned pregnancies. While one type of cancer may be slightly more likely when you're on the pill, it may actually decrease your risk for several others.
A meta-analysis of 20 studies between 1970-1991 found that oral contraceptive use was linked to reduced risk of ovarian cancer that increased with the duration of use. Women who took the pill for one year saw a 10-12 percent decrease in risk, and those who took it for over five years had a 50 percent lower risk, even 10 years after stopping. Another analysis found that risk of endometrial cancer decreased for women on the pill, and the longer they took it, the lower their risk was. The paper directly credits oral contraceptives with preventing 200,000 cases of endometrial cancer between 2005 and 2014. And yet another found that the risk of colorectal cancer was 36 percent lower for women who had used the pill. You should always discuss the risks and benefits of any medication or treatment with your doctor, of course, but the takeaway is that for many, the benefits of birth control are totally worth it.
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