A new study finds that the use of low-dose oral contraceptive pills does not significantly increase a woman’s chances of having a stroke. However, for women who smoke and use oral contraceptives, the study found a higher risk of hemorrhagic stroke. The report was published in Thursday’s New England Journal of Medicine.
The researchers, led by Doctor, identified strokes that occurred in the 1.1 million female members of the California Kaiser Permanente Medical Program between the ages of 15 to 44 years old. The researchers considered both types of stroke: ischemic stroke, in which there is decreased blood flow to the brain due to a clot or narrowed artery; and hemorrhagic stroke, in which there is bleeding into the brain tissues due to a ruptured blood vessel or an aneurism.
The incidence of stroke identified in this population was a very low 11.3 per 100,000 woman-years. 295 women with stroke were randomly matched with members who had not had stroke, and all were interviewed about their use of oral contraceptives.
The odds ratio for ischemic stroke among current users of oral contraceptives was 1.18, as compared to former users or women who had never used oral contraceptive drugs. The risk factor for hemorrhagic stroke was 1.14. For women who smoke and use oral contraceptive drugs, the study found an odds ratio of 3.64.
Previous studies had linked oral contraceptive use to an increased risk of stroke, however those studies were based on oral contraceptives that contained more estogen than in today’s “low-dose” pills.