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-W. Bradford Wilcox
Associate Professor of Sociology, University of Virginia
Feminists consistently urge legislators to continue making access to contraception universal and free. The more women on the pill, the better “liberated” we all are. But a new study out of Denmark should make policymakers pause before jumping on the “free birth control for all” bandwagon.
In a paper accepted by the British Journal of Pharmacology, researchers Lene Andersen et al. study the effect of oral contraceptive use on the risk of developing glioma, a type of cancerous brain tumor. The researchers establish the background for their study by pointing out that use of hormonal contraceptives “slightly increases” the risk of several types of cancer, including cervical cancer, breast cancer, and hepatocellular carcinoma. In spite of this increased risk, however, “few studies have examined any link with risk of central nervous system tumors.” This lack of research is a concern, because “[g]liomas are the most common type of malignant brain tumors in the Nordic countries.” Previous studies focusing on the link between glioma and oral contraceptive use have shown little association, but the use of such findings is limited because the subjects were postmenopausal women.
The researchers obtained their data from a host of national registries tracking Danish cancer patients. They reduced their sample to women between the ages of 15 and 49 “with a histologically verified first diagnosis of brain glioma during 2000-2009.” Subjects had no previous instance of cancer. “Ever use” of oral contraceptives was defined as women who had taken two prescriptions or more, while “non-use” was defined as fewer than two prescriptions. For IUDs, “ever use” was one prescription. The researchers also defined “recent use” as one prescription or less taken in the past 2-5 years. Type (combined estrogen-progestagen, progestagen-only, or mixed use) was also considered.
In the end, the sample “consisted of 317 cases and 2,126 controls, which were similar for distribution of age, parity, and years of schooling.” The findings? “Long-term use of hormonal contraceptives was associated with an increased risk of glioma that increased with duration of use.” In their sample, almost 60% of the sample and 50% of the controls had ever used hormonal contraceptives. The risk of developing glioma was higher for current or recent use (Odds Ratio of 1.7; 95% Confidence Interval: 1.3-2.4). Moreover, “the OR for glioma was elevated with use of combined estrogen and progestagen (OR, 1.4; 95% CI: 1.0-1.8) and highest for pregestagen-only (OR, 2.8; 95% CI: 1.6-5.1).”
The authors summarize their findings: “Long-term use of hormonal contraceptives was associated with an increased risk of glioma that increased with duration of use. The risk estimates were particularly elevated for use of progestagen-only.” More recent use was associated with increased risk of glioma. Given “the extensive use of hormonal contraceptives,” the researchers write, “our finding merits further investigation.”
Indeed. In a world in which hormonal contraceptives are often prescribed to girls as soon as they reach menarche, studies such as these should cause policymakers to say “hold on” before cheerfully handing out more free pills.
(Lene Andersen et al., “Hormonal Contraceptive Use and Risk of Glioma among Younger Women a Nationwide Case Control Study,” accepted article, British Journal of Pharmacology [October 26, 2014] 10.1111/bcp.12535, Web.)