The findings of new research suggests that long-term use of some birth control pills may cause women to face an increased risk of developing brain tumors.
In a study published this month in the British Journal of Clinical Pharmacology, researchers from the University of Southern Denmark and Odense University Hospital found an association between the use of hormonal contraceptives containing estrogen, progestin or both and an increased risk of a form of brain tumor known as glioma.
Long-term use of birth control pills appeared to nearly double the risk of problems for women, researchers warned. However, the overall risk of developing brain tumors remains small and the study indicates that the benefits of birth control pills may outweigh the risk.
Researchers used the national administrative and health registries in Denmark, looking at data on women between the ages of 15 and 49 who were diagnosed with glioma between 2000 and 2009. They categorized their findings based on the types of oral contraception used and the length of time the women used them.
Overall, researchers found that any woman who ever used hormonal contraception faced a 50% increased risk of glioma. When they used the pill for five years or longer, the risk increased to 90%. However, women who used progestin-only faced an increased risk of 140%. That risk increased substantially if progestin-only birth control was all they had ever used.
“It is important to keep this apparent increase in risk in context,” said the lead researcher, Dr. David Gaist. “In a population of women in the reproductive age, including those who use hormonal contraceptives, you would anticipate seeing 5 in 100,000 people develop a glioma annually, according to the nationwide Danish Cancer Registry.”
Gaist said that while the findings were statistically significant, the benefits of birth control pills still far outweighed the risk of brain tumors. However, Gaist said that such research was still important and should be ongoing, so women had access to all the information necessary to select the most appropriate form of birth control.