Heart disease has long been the top killer of women in the United States, but new research suggests uterine fibroids, which many may not even be aware they have, could be putting them at a significantly greater risk.

A large, 10-year study found that women with leiomyomas had an 81% higher long-term risk of heart disease than those without the common condition. Women with fibroids — generally benign tumors that can form on or in the uterus — also had higher individual risks of cerebrovascular, coronary artery and peripheral artery diseases a decade after diagnosis.

The study involved more than 2.7 million U.S. women and was led by scientists at the University of Pennsylvania Perelman School of Medicine. It was published Wednesday in the Journal of the American Heart Association.

“We do hope that our study adds to this growing evidence that reproductive health may provide important insights into cardiovascular health,” said lead author Julia DiTosto, a doctoral candidate in epidemiology at Penn. “There is a need for more information on how exactly, biologically, these conditions are related and also identifying potential strategies for cardiovascular prevention.”

Fibroids are a vastly underfunded area of women’s health research. In 2024, the National Institutes of Health awarded $17 million toward the study of fibroids, up from $14 million in 2023. By comparison, NIH records show $28 million went to endometriosis, $59 million to menopause and $740 million to breast cancer. Previous studies on fibroids and heart disease were “sparse and inconclusive,” DiTosto and her co-authors wrote.

In this new study, researchers scoured a health care database that contained patient records from 2000 through 2022. About 450,000 women had been diagnosed with fibroids and more than 2.2 million had not. Patients’ average age was 41.

Researchers calculated patients’ risks of heart disease at one, three, five and 10 years. For every specific condition studied — including stroke and heart attack — as well as overall heart disease, women with fibroids had a higher risk at each follow-up period.

Women with fibroids had an elevated risk of heart disease across all age groups, races and ethnicities. However, women younger than 40 had a stronger link between fibroids and heart disease — and a 251% higher risk at 10 years. This was a particularly surprising finding, DiTosto said, given that older age is a risk factor for heart disease.

Fibroids are known to disproportionately affect Black women, who are often diagnosed at a younger age, endure more severe symptoms and have larger or more numerous tumors. However, the study found that risk of heart disease was lowest among Black women with fibroids. Risk was both highest and most imprecise among Asian women at one, three and five years. At 10 years, risk was highest among Hispanic women.

“Fibroids are not just a concern for gynecologic health,” DiTosto said. “They may also influence broader conditions, and it’s important to think of health comprehensively.”

How fibroids may increase heart disease risk

Fibroids are exceedingly common, plaguing an estimated 26 million U.S. women of childbearing age. According to the federal Office on Women’s Health, anywhere from 20% to 80% of women will develop fibroids by age 50.

A woman may have more than one fibroid at a time and in different places throughout her uterus. A growth can be as small as a seed or as large as a watermelon, making a woman appear pregnant. Treatments range from minimally invasive procedures, such as a radiofrequency ablation, which uses heat to damage tumor tissue, to a hysterectomy, and new fibroids may grow even after old ones have been surgically removed.

In most cases, women are asymptomatic and unaware they have fibroids until they undergo a pelvic exam or imaging. Dr. John Petrozza, co-director of the Integrated Fibroid Program at Massachusetts General Hospital, said women who have fibroid symptoms often find them debilitating.

“They cause a lot of expenditures of health care dollars dealing with the symptoms related to fibroids, which include heavy menstrual bleeding, iron-deficiency anemia, pelvic pressure, bowel symptoms, bladder symptoms, infertility,” said Petrozza, who wasn’t involved in the study.

Fibroids feed off two hormones produced by women of reproductive age — estrogen and progesterone — which may be a clue to their link to heart disease, Petrozza said.

“Those hormones can cause other things, like smooth muscle cell proliferation, fibrosis, calcification, which has an impact on your vascular system,” he said. “And then if you get heavy periods because of the fibroids and you start to get iron-deficiency anemia, that has a stress-like effect on your blood pressure.”

Such symptoms can place stress on the whole body, he said, which, in turn, can trigger biological changes, including inflammation.

Fibroids are common in people with obesity, who may have other underlying conditions that increase their risk of heart disease.

“There is a potential cause and effect that needs to be explored a little bit more, but that, in my mind, is how I envision this being connected,” Petrozza said, later adding, “You get this chain reaction that can cause atherosclerotic cardiovascular disease, which has a link to heart attacks and strokes.”

Who’s at risk of developing uterine fibroids?

The study’s observational nature was one of its major limitations, DiTosto said. She and her team analyzed patient records from Optum’s Clinformatics Data Mart, which was designed for insurance billing, not clinical research.

While the database allowed researchers to explore a large sample size and long-term outcomes, it didn’t account for more granular information such as patients’ size, number and location of fibroids, “which can give more information on the mechanisms behind how fibroids and cardiovascular disease might be related,” DiTosto said.

The study also didn’t cover the possible effects of fibroid removal on a person’s risk for heart disease.

Additionally, the database included only privately insured patients, who may have had access to better fibroid diagnosis and treatment than their uninsured peers.

Women with a family history of the tumors are more likely to have them. Other risk factors include older age (through menopause), obesity, high blood pressure, vitamin D deficiency, consuming alcohol, eating a diet high in red meat, not having been pregnant, and beginning menstrual periods at an early age.

Petrozza said fibroids are often asymptomatic, but women should be careful not to dismiss warning signs.

“If you notice any changes in your menstrual flow, if you notice increasing abdominal girth, if you just don’t feel right in your pelvis, if you’re going to the bathroom more often, if you’re having difficulty conceiving, those are subtle signs of uterine fibroids,” he said. “That should warrant you bringing this up with your primary care or your gynecologist.”

This article was originally published on NBCNews.com