Hormone replacement therapy (HRT), widely used to alleviate menopause symptoms such as hot flashes and night sweats, may increase the risk of heart disease and blood clots in some women, according to a new study published in The BMJ.

The research, led by Therese Johansson, a doctoral student at Uppsala University in Sweden, revealed that oral hormone therapies, particularly estrogen/progestin pills, elevate the risk of heart disease by 21% and life-threatening blood clots by 61%. Tibolone, a synthetic hormone, was found to increase the risk of heart disease by 46% and nearly double the likelihood of stroke and heart attack. However, tibolone did not increase the risk of blood clots, underscoring the varied effects of different hormone therapies on cardiovascular health.

To assess the risks associated with HRT, researchers examined data from over 919,000 healthy Swedish women aged 50 to 58 between 2007 and 2020. The women were categorized based on the type of hormone therapy prescribed, while a separate group received no hormone treatment. Over a two-year observation period, more than 24,000 heart-related health issues were reported.

The study found that oral estrogen/progestin therapies and tibolone contributed to significant cardiovascular risks, with an estimated 11 additional cases of heart-related problems for every 1,000 women treated annually. Notably, transdermal hormone therapies, including patches, gels, and creams, did not increase the risk of heart disease. However, they were linked to a higher likelihood of blood clots, highlighting the need for personalized approaches to HRT.

The findings shed light on the mechanisms behind these risks. Oral estrogen is metabolized in the liver, where blood coagulants are produced, potentially increasing clot formation. Transdermal therapies bypass the liver, which may explain their reduced impact on clotting risks.

While tibolone is not approved in the United States, its use in Sweden has been declining. Even so, researchers estimated that in 2018, approximately 1,000 Swedish women began tibolone treatment, potentially resulting in one stroke or heart disease case. Johansson’s team emphasized the importance of ongoing research to better understand the effects of hormone therapy on cardiovascular health, especially for menopausal women.

These findings underscore the need for caution when prescribing HRT. Women considering hormone therapy are encouraged to consult their healthcare providers to weigh the potential benefits and risks. By tailoring treatments to individual needs, healthcare professionals can help ensure safer management of menopausal symptoms.