New study finds correlation between long term birth control use and rare brain tumor

A new study has found a correlation between hormonal birth control and a type of brain cancer.

A new study has found that certain types of birth control may be linked to an increased risk of developing glioma, a rare type of brain cancer.

The Danish research project found that women under the age of 50 with glioma were “90 percent more likely to have been using hormonal contraceptives for five years of more, compared with women from the general population with no history of brain tumor,” said Dr. David Gaist, lead author of the study, according to CBS News.

The researchers reported that use of hormonal contraceptives did increase the risk of developing glioma, with a sharper increase the longer the duration of use.The study also noted that the risk seemed to increase for women using pills with the hormone progestogen rather than estrogen.

It is important to point out that the researchers found only a correlation. The researchers could not isolate a cause and effect relationship and Gaist stresses that the results “need to be put into context.” The most important context is the rarity of glioma.

Only five of every 100,000 Danish women between the ages of 15 and 49 develop glioma each year. This figure includes women who use oral contraceptives.

“An overall risk-benefit evaluation favors continued use of hormonal contraceptives,” said Gaist.

The study looked at 317 cases of glioma in women ages 15-49 from 2000 to 2009. Among them, 60 percent had used oral contraceptives. This group was then compared to 2,100 women without glioma, about 50 percent of whom used oral contraceptives.

Dr. Evan Myers is a professor of obstetrics and gynecology at Duke University Medical Center. Myers told CBS the study was “really well-done.”

However, Myers also points out that the lack of a cause and effect relationship means further research is required. He encouraged future research to focus on other indirect factors that may play a role in the increased risk for glioma.

“Even if hormonal contraception does increase the relative risk of glioma, the absolute risk — the actual increase in chances of having a glioma diagnosed — is quite small,” said Myers.

“Without going through the math, it’s about 8.5 [cases] per million.”