Are you someone who prefers to pop a morning-after pill or other contraceptive pills after unprotected intercourse? Then this could be a hard pill to swallow.
A new study has found a higher risk of heart attack and stroke associated with hormonal contraceptives. Among the many birth control methods, an estimated 250 million women worldwide rely on hormonal contraception. Though previous studies have suggested a potential increased risk of ischaemic stroke and heart attack with their use, the findings were inconsistent.
However, a new study from Denmark, published in The BMJ, has added to the evidence. The highest risk estimates were for oestrogen-containing products, in particular the vaginal ring and skin patch.
The researchers said that the absolute risk remains low, however, given the widespread use of such contraceptives, they stressed that healthcare experts should consider these potential risks when prescribing them.
The previous studies also lack evidence on the effects of different hormone combinations, how they are taken (eg, pills, implants, injections, vaginal rings, or skin patches), and for how long. The researchers tracked the national prescription records of more than two million Danish women aged 15-49 from 1996 to 2021. The types of contraceptives included in the study were combined estrogen-progestin pills, vaginal rings, patches, progestin-only pills, intrauterine devices, subcutaneous implants, and intramuscular injections.
Women who had a history of blood clots, cancer, liver disease, kidney disease, polycystic ovary syndrome, endometriosis or infertility treatment, used psychiatric medication, or hormone therapy, or had undergone a hysterectomy were excluded from the study. The cases of ischemic stroke and heart attack were recorded. They also looked at other potentially influential factors such as age, education level, and existing conditions such as high blood pressure and diabetes were taken into account.
The combined oestrogen-progestin pill, which is the most commonly used hormonal contraceptive, was linked with double the risk of ischaemic stroke and heart attack. This mean one extra stroke for every 4,760 women using the combined pill for one year, and one extra heart attack for every 10,000 women per year of use.
The progestin-only contraceptives, such as pills and implants, carried a slightly elevated risk, however, lower than the combined pills. Non-oral combined contraceptives, such as the vaginal ring and patch, had higher associated risks, with the vaginal ring increasing ischaemic stroke risk 2.4-fold and heart attack risk 3.8-fold, while the patch increased ischaemic stroke risk 3.4-fold.
The only hormonal contraceptive not linked to an increased risk was the progestin-only intrauterine system, making this option safer for cardiovascular health. The duration of use also did not seem to influence the risk.
However, this is an observational study so no firm conclusions can be drawn about cause and effect. “Although absolute risks were low, clinicians should include the potential risk of arterial thrombosis in their assessment of the benefits and risks when prescribing hormonal contraceptive method,” the authors said.
Therese Johansson at the Swedish Institute of Technology stated that these diseases are rare, especially in young women. However, the side effects are serious, given that approximately 248 million women use hormonal contraceptives daily.