You've seen it in the news a lot lately, but you’re not quite sure what it means — endometriosis. Girls star Lena Dunham recently dedicated an entire issue of her Lenny newsletter to the disorder; it affects only about 10 percent of women, but can go undetected for decades. That’s a problem because, in addition to being painful and unpleasant, it may increase a woman’s risk for coronary heart disease. A new study published in Circulation: Cardiovascular Quality and Outcomes suggests why.

Endometriosis occurs when the tissue that normally lines the inside of the uterus starts to grow outside of it, including in the ovaries, bowel, and pelvic wall. The tissue still functions the same, though, meaning it bleeds every time a woman menstruates. Since the shedding tissue has nowhere to go, it becomes trapped, which can eventually cause cysts, organ damage, and even fertility problems. What the new study finds is that women who choose to treat the condition by undergoing a hysterectomy — their uterus, cervix, and ovaries are all removed — before they turn 50 could elevate their risk for heart disease.

Study co-author Dr. Stacey A. Missmer, an associate professor of obstetrics, gynecology, and reproductive biology at Brigham and Women’s Hospital in Boston, told Medical Daily that she and her colleagues knew there was a potential link between the two conditions. In fact, this relationship has already been well-reported. Prior studies have connected endometriosis with three heart disease risk factors: chronic inflammation; oxidative stress, a result of the body producing more reactive molecules than it can fend off; and an atherogenic lipid profile, or fatty plaque in the arteries. But to the team’s knowledge, this is the first study to investigate the possible mechanisms that underlie the association.

They analyzed data from 116,430 women who enrolled in the Nurses’ Health Study II in 1989. Participants answered questions that had to do with their demographic, such as age, sex, and education, plus others related to their medical, lifestyle, and reproductive histories. In 1993, women were asked if they had been diagnosed with endometriosis. If they answered yes, researchers then asked for the specifics and whether the diagnosis was confirmed by laparoscopy — the gold standard for diagnosis of the disorder.

To assess for heart disease, the authors looked at reported cases of fatal and non-fatal heart attack, angina or chest pain, and any surgery meant to restore blood flow to the arteries, including bypass and angioplasty.

Results associated endometriosis with a higher risk of heart disease, especially among younger women. What’s more, the authors believe a portion of the association could be explained by treatments such as hysterectomy and oophorectomy, where only the ovaries are removed; removing one ovary didn’t seem to increase risk as much as removing both did. Surgeons who perform these procedures essentially induce menopause, which could account for the higher incidence of disease in patients younger than 50, especially since women who elected hysterectomy after their 50th birthday were not at equal risk.

That said, the study has several limitations. Most importantly, Missmer and her team only used laparoscopically-confirmed cases of endometriosis instead of including physician-diagnosed cases, Dr. Sherry Thomas, an urogynecologist and surgeon based in Thousand Oaks, Calif., told Medical Daily.

The reasons behind this decision are two-fold, according to the study: One, the surgical reports were more valid than clinical records: Without surgical confirmation, there’s a chance a woman was misdiagnosed. There was also a low proportion of women reporting a clinical, but not surgically-confirmed endometriosis, Missmer said. So she doesn’t think it would have impacted the study to include the latter cases, though, she added, it’s still important girls and women with endometriosis and the scientists who study it know this is a possibility.

It’s important to note, too, that hysterectomy is not the first line of treatment for women who have the disorder, Thomas said, and it’s not foolproof either. There is a 50 percent chance the pain will recur after the procedure. Before they even get to that point, women may choose other pain-relieving options, such as hormonal contraception and NSAIDs like Ibuprofen. Missmer added there is emerging evidence that complementary medicine such as acupuncture and physical therapy focused on the pelvic floor can be equally effective.

The bottom line: Endometriosis could elevate risk for heart disease, but the study doesn’t make it explicitly clear whether it’s so much the disorder as it is the more severe treatments, Thomas said. She does agree with Missmer, however, that women with endometriosis should adopt heart-healthy lifestyles.

“Exercise and diet beat everything,” Thomas said.

Missmer further recommends that women get screened by their doctors for heart disease and familiarize themselves with its symptoms because, endometriosis or not, heart disease remains the number one killer of women.

And that ultimately goes back to the point Dunham was trying to make in her newsletter: We need to dedicate more time and resources to the disorder to really understand how it works and what it means for women.

“No one is just her reproductive system or just her cardiovascular system,” Missmer said. “Whenever we're considering health, we need to think about the whole woman — her whole body and across her entire lifetime.”

Source: Missmer S et al. Endometriosis and Risk of Coronary Heart Disease. Circulation: Cardiovascular Quality and Outcomes. 2016.