Study: Women With Endometriosis May Have Higher Risk of Stroke

New research emphasizes that women with endometriosis should be aware of additional health risks.

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Women with endometriosis may have a higher risk of stroke, suggests new research funded by the National Institutes of Health. The findings have the potential to impact a lot of people—more than 11% of women in the U.S. alone are believed to have endometriosis.

The study was published last week in Stroke, a journal from the American Stroke Association, and found that women with endometriosis had a 34% higher risk of having a stroke than those without the chronic inflammatory condition. (The researchers did not have access to data on people who were assigned female at birth and are not living as women.)

"These findings suggest that women with a history of endometriosis may be at higher risk of stroke," study senior author Stacey Missmer, ScD, a professor of obstetrics, gynecology, and reproductive biology at Michigan State University College of Human Medicine, said in a press release. "Clinicians should look at the health of the whole woman, including elevated blood pressure, high cholesterol, and other new stroke factors, not only symptoms specifically associated with endometriosis, such as pelvic pain or infertility."

Endometriosis occurs when tissue similar to that which lines the uterus—or the endometrium—grows outside of the uterus, commonly on the ovaries, fallopian tubes, or on the bowels or bladder. This can cause extreme pain, often timed with your period, as well as infertility, extremely heavy periods, and digestive problems, among other things.

According to study authors, treatments that are often used to relieve symptoms—including hysterectomy (surgical removal of the uterus) and/or oophorectomy (surgical removal of the ovaries), and postmenopausal hormone therapy—made up the largest proportion of stroke risk among women with endometriosis.

Here, experts help break down what this research means for people with endometriosis—and how this may influence how the disease is treated.

Endometriosis Associated With Increased Risk of Stroke

Overall, "there has been very limited research on endometriosis and risk of stroke," lead study author Leslie V. Farland, ScD, an assistant professor in the department of epidemiology and biostatistics at the University of Arizona, told Health.

That lack of research is what prompted Farland and her colleagues to look into how endometriosis might impact stroke risk—especially because prior research from her team "observed an association between endometriosis and increased risk of cardiovascular disease endpoints including hypertension, high cholesterol, and myocardial infarction," said Farland.

For the study, Farland and her team analyzed data from 112,056 women between the ages of 25 and 42, who were enrolled in the Nurses' Health Study II—one of the largest investigations into the risk factors of major chronic diseases in women. Of those more than 100,000 women, 5,244 had clinically-diagnosed endometriosis.

The researchers analyzed data that was collected every two years during a 28-year period, looking for other confounders or risk factors for stroke, including alcohol intake, body mass index (BMI), oral contraceptive use, and diet, among other factors. Among all participants, 893 women had a stroke during that time.

Women diagnosed with endometriosis were found to have a 34% greater risk of having a stroke, compared to women who did not have endometriosis; and the greatest risk of stroke was linked to women who had a hysterectomy and/or oophorectomy (39%) and those who received postmenopausal hormone therapy (16%). The researchers didn't find a link between endometriosis and stroke when it came to other factors like age, infertility history, BMI, or menopausal status.

Certain Treatments May Lead to Higher Risk

It's not entirely clear why endometriosis may raise the risk of stroke, and Farland noted that the study didn't explore the reason for the connection—it simply found a link. The study also wasn't able to parse apart the risk of having different types of stroke, like ischemic stroke and hemorrhagic stroke, she said.

However, researchers have some theories. "We hypothesize that it may be a combination of inflammation, increased risk of cardiovascular disease risk factors, such as hypertension and high cholesterol, and possibly earlier age at menopause, induced by gynecologic surgery," said Farland.

Because the majority of strokes among women with endometriosis occurred in those who underwent surgical procedures or hormone therapy, those are likely factors—but it's also unclear why, Missmer told Health. She theorizes that—though the treatments are meant to reduce symptoms and inflammation—the procedures and treatments themselves could also raise the risk of stroke.

"There are circumstances when a hysterectomy and/or oophorectomy is the best choice for a woman, however, we also need to make sure that patients are aware of the potential health risks associated with these procedures," Missmer said in the press release. "Other research also suggests that hysterectomy is associated with elevated stroke risk even if there is no history of endometriosis."

Although previous research linking hysterectomy and/or oophorectomy did not look into causes, experts believe that it's the menopause, triggered by the procedures, that can impact the risk of stroke.

"The data is limited on whether hysterectomy alone has any impact on cardiovascular health," Angela Chaudhari, MD, chief of gynecology and gynecologic surgery at Northwestern Medicine, told Health. "However, there is data to suggest an increased risk of cardiovascular events such as heart disease and stroke are associated with oophorectomy that results in surgical menopause."

The distinction between hysterectomy alone and a hysterectomy and/or oophorectomy is an important one. A hysterectomy alone should not have an effect on hormone production; but a hysterectomy with an oophorectomy, or an oophorectomy alone, will affect hormone levels, as ovaries are the main source of estrogen production in the body.

"Hysterectomy when combined with bilateral oophorectomy can increase risk of stroke, particularly in younger patients for which the surgery would result in premature menopause," Tamisa Koythong, MD, assistant professor of obstetrics and gynecology and minimally invasive gynecologic surgery at Baylor College of Medicine, told Health. "However, hysterectomy itself without removal of ovaries does not have this same increased risk— and that is because a hysterectomy should not affect a woman's hormonal status, as that is completely dependent on ovarian function."

Postmenopuasal hormone therapy—or hormone replacement therapy—which can also affect hormone levels. "There is an increased risk of cardiovascular disease and stroke in women placed on hormone replacement therapy, specifically a combined estrogen-progesterone combination," said Dr. Chaudhari.

But overall, "we don't completely understand this risk with long-term health outcomes," said Missmer, adding that "more research is needed."

The Importance of Whole-Body Care and Prevention With Endometriosis

Although patients and their healthcare providers should be aware of additional health risks of endometriosis, experts stress that the overall risk of stroke in women is low.

"While we observed that women with endometriosis had a relative risk of stroke that was higher than women without endometriosis, the absolute risk of stroke in women with endometriosis is still low," Dr. Farland said.

"This is not a reason to panic," added Missmer. "It does not mean that everyone who has endometriosis is going to get a stroke." She referenced other, greater risk factors for stroke, like smoking, which increases stroke risk by 63%. "We're not seeing effects anywhere close to that for endometriosis." said Missmer.

However, the research still emphasizes that people with endometriosis need to pay attention to their whole-body health. "The take home message is that those with endometriosis need to be aware of all the signs and symptoms related to their health across the body, not just pain and infertility," said Dr. Missmer. "Anything related to cardiovascular or cerebrovascular disease needs to be on their radar."

The same goes for treatment options for endometriosis. "[Doctors] need to be cognizant of what surgical intervention we're discussing with patients, taking into account their age," said Dr. Koythong. "[This is] part of the reason why treatment of endometriosis is so difficult. We have to balance treatment of the disease itself while also considering the patient as a whole, who is still at risk for other chronic diseases."

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