A large-scale study from Denmark published in The BMJ has found that certain hormonal contraceptives may elevate the risk of stroke and heart attack. The study, which analyzes prescription records, provides more accurate risk assessments for various contraceptive products compared to previous research.
Estrogen-containing contraceptives, especially the vaginal ring and skin patch, were found to carry the highest associated risks. Despite these findings, the researchers emphasized that the overall risk remains low. However, given the widespread use of these products and the severity of stroke and heart attack, the study suggests that healthcare providers should weigh these risks when prescribing hormonal contraceptives.
Globally, an estimated 250 million women use hormonal contraception. Prior studies have raised concerns about an increased risk of ischemic stroke and heart attack linked to hormonal contraceptive use, but results have been inconsistent. There has also been limited evidence regarding the effects of different hormone combinations, delivery methods (e.g., pills, patches, injections, and implants), and the duration of use.
To address this gap, researchers analyzed national prescription records for over two million Danish women aged 15–49 from 1996 to 2021, comparing those who used hormonal contraception to those who did not. The study specifically examined combined estrogen-progestin pills, vaginal rings, patches, progestin-only pills, intrauterine devices (IUDs), subcutaneous implants, and intramuscular injections.
Women with a history of blood clots, cancer, liver disease, kidney disease, and other medical conditions were excluded from the study. The researchers tracked cases of ischemic stroke and heart attack, adjusting for other factors such as age, education level, and pre-existing conditions like high blood pressure and diabetes.
The results showed that the most commonly used hormonal contraceptive, the combined estrogen-progestin pill, was associated with double the risk of ischemic stroke and heart attack. Specifically, it resulted in one additional stroke for every 4,760 women using the pill for one year, and one additional heart attack for every 10,000 women per year of use.
Progestin-only contraceptives, including pills and implants, posed a slightly elevated risk, but lower than the combined pill. Non-oral contraceptives, such as the vaginal ring and patch, presented significantly higher risks. The vaginal ring was linked to a 2.4-fold increase in ischemic stroke risk and a 3.8-fold increase in heart attack risk, while the skin patch increased ischemic stroke risk by 3.4 times.
The progestin-only intrauterine system (IUS) stood out as the only hormonal contraceptive not associated with an increased cardiovascular risk, making it a safer option for those concerned about heart health. The duration of contraceptive use did not appear to affect these risks.
As an observational study, the research cannot establish causality, and the authors acknowledge the possibility that unmeasured factors could have influenced the results. However, given the nationwide scope of the study and the use of high-quality registry data, the findings are considered robust.
The researchers urge clinicians to factor in the potential risks of arterial thrombosis when assessing the benefits and risks of hormonal contraceptive methods for their patients.
While cardiovascular events such as strokes and heart attacks are rare in young women, Therese Johansson from the Swedish Institute of Technology, writing in an editorial accompanying the study, underscores the seriousness of these side effects. With approximately 248 million women using hormonal contraception worldwide, Johansson calls for public education campaigns to help women make informed choices about their contraceptive options. She also advocates for healthcare provider training to ensure evidence-based counseling and policy changes to make safer alternatives accessible, especially in low-resource settings where cardiovascular risks may go undiagnosed or untreated.
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