Danish case control study links oral contraceptives with glioma

1. Hormonal contraception use was more prevalent among women who developed glioma, a brain tumor, to women without glioma.

2. The magnitude of this association was greatest among women taking progestin-only hormonal contraception.

Evidence Rating Level: 3 (Average)  

Study Rundown: Gliomas, the most common type of malignant brain tumor, occur more often in men than women, leading researchers to speculate whether estrogen and/or progesterone play a protective role in the development of glioma. Previous studies examining the link between use of hormonal contraception and glioma found no association, but these studies were limited to postmenopausal women and used self-reported data. In this large, population-based study, researchers evaluated the association between hormonal contraception use and glioma risk in reproductive aged women.

Ever use of hormonal contraceptives was associated with a 1.5 fold increase in the odds of glioma. The association was greatest in those taking progestin-only pills, such as the minipill.  A major strength of this study was the use of the Danish National Registry, which contains prospectively-collected, detailed and long-term drug histories for each participant. The major limitations of this work were its case-control design. In addition, it is unknown whether it was the need for hormonal contraceptives (e.g. endometriosis, dysmenorrhea, menstrual migraines) or the use of the contraceptives that were associated with glioma. For example, a patient may have been diagnosed with menstrual migraines and prescribed progestin-only hormonal contraception (estrogen is contraindicated in catamenial migraines) but in reality had headaches from her undiscovered brain tumor. As it stands, the results of this early, Level III study should not guide patients or practitioners to change their recommendations regarding hormonal contraception. Further examination of this association is necessary in longer-term, larger and prospective investigations in a more ethnically and geographically diverse population.

Click to read the study in the British Journal of Clinical Pharmacology

Relevant Reading: Exogenous and Endogenous Hormones in Relation to Glioma in Women

Study Author, Dr. David Gaist, MD, PhD, talks to 2 Minute Medicine: Odense University Hospital, Department of Neurology:

“These figures need to be put in context. Glioma is very rare. In Denmark, it afflicts approximately 5 younger women (ages 15-49) per 100,000 women that age per year, a figure which includes women who take hormonal contraception.”

In-Depth [case-control study]: Researchers identified women ages 15-49 from the national Danish health registry with first time diagnosis of glioma (n=317). For each case, eight age-matched controls were identified (n=2126). Participants were categorized by hormonal contraceptive use, type and duration of use.

Compared to women without glioma, a higher proportion of women with glioma reported ever using contraceptives (58.7 vs. 50.1%, OR=1.5, CI=1.2-2.0). The odds of glioma were highest among women who used progestin-only pills (OR=2.8, OR 1.6-5.1). Women who used hormonal contraception for ≥5 years experienced higher odds of glioma (OR=1.9, 95% CI=1.2-2.9), however test of trend was not significant (p=0.06).

More from this author: Hormonal IUD more effective than copper IUD, Post-partum Implanon offers long-term contraception for high risk women, Phthalate exposure associated with later puberty in females, Social media effective adjunct for contraception education, Autism associated with air pollution exposure during pregnancy

Image: PD

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