Obese women who take oral contraceptives might have an increased risk of stroke.
According to researchers led by Dr. Jonathan Coutinho of the Academic Medical Center at the University of Amsterdam in the Netherlands, obesity and contraceptive use can be linked to a woman's risk of cerebral venous thrombosis (CVT), which is an extremely rare type of stroke.
The researchers compared 186 male and female patients with CVT to 6,134 healthy adults of similar age. Overall, they found that CVT patients were generally younger than their healthy counterparts and were more likely to be female. CVT patients were also more likely to have a history of oral contraceptive use and cancer.
When the researchers looked at oral contraceptive use specifically, they found that the combination of birth control pills and obesity, which was measured using body mass index (BMI), led to an almost 30-fold increased risk of CVT in comparison to normal weight women who did not take oral birth control. The researchers did not find an association between obesity and CVT risk in men and women who were not on oral contraceptives.
The researchers cited only one other study that had found an association between CVT and obesity. In that study, which included a small sample of 22 participants, the researchers reported that CVT tended to be more common in children who were obese. The study, however, did not account for confounding variables.
Coutinho and his colleagues hope that their findings provide a much better understanding of the association between birth control combined with obesity in women and CVT risk.
"The increased risk of VTE [venous thromboembolism] and CVT associated with oral contraceptives in the presence of obesity might make physicians reluctant to prescribe oral contraceptives to obese women," the authors wrote. "However, although the relative risks are increased substantially, the absolute risks of CVT are small. Moreover, withholding oral contraceptives may lead to an increase in unintended pregnancies and, thus, the number of pregnancy-related thrombosis cases. Nevertheless, obese women should be informed about the increased risk of thrombosis if they use oral contraceptives, especially if other risk factors are present."
Chirantan Banerjee, of the Medical University of South Carolina, Charleston, pointed out in a related editorial that although the increased risk of CVT appears to be relatively small, women should be fully aware about the risks involved.
"The authors correctly point out that despite the manifold increased relative risk, the absolute risk of CVT in obese women taking OCs [oral contraceptives] still remains low and should not preclude OC use among them," Banerjee wrote. "Use of OCs has also been associated with increased risk of arterial ischemic stroke in obese women. Better counseling and education of obese women informing them of the increased risk would be prudent, as would be consideration of alternate nonhormonal OC options."
There are many alternative birth control options, such as intrauterine devices, that have not been tied to an increased risk of CVT.
The study's findings were published in JAMA Neurology.
