A new, large prospective study analyzed data of 112,056 women over 28 years.
Using models to adjust for potential confounding factors, the study concluded that women with endometriosis had a 34% greater risk of stroke.
About 10% of women of reproductive age are known to have endometriosis, which is a chronic and often painful condition where tissue similar to the tissue that lines the uterus grows outside that organ.
Earlier research, including this 2016 study, has found endometriosis to be associated with an increased risk of coronary heart disease.
“Prior research from our team observed an association between endometriosis and increased risk of hypertension, high cholesterol, and myocardial infarction,” Leslie Farland, Sc.D., first author of the study and assistant professor of epidemiology and biostatistics at the University of Arizona in Tucson, explained in an email to Medical News Today.
“Given that these conditions are associated with stroke risk, we wanted to understand if women with endometriosis also had an elevated risk of stroke,” Prof. Farland said.
Endometriosis and stroke risk
The researchers designed their study to overcome limitations found in other studies looking at endometriosis and the risk of stroke, which included following up with participants over short durations and limited accounting for potential confounding factors.
For their study, the researchers looked at participants of the Nurses’ Health Study II (NHSII): 116,429 women who were nurses between the ages of 25 and 42 in 1989. Participants in the NHSII were mailed questionnaires every two years through 2017 that asked questions about diseases and risk factors.
Next, researchers excluded NHSII participants who had a history of stroke, myocardial infarction, cancer (other than nonmelanoma skin cancer) or a coronary artery bypass grafting before June of 1989 or who had an endometriosis diagnosis that was not confirmed by laparoscope. That left 112,056 participants, with 5,244 of those having endometriosis. Among the selected participants, there were 893 incidents of strokes over 28 years of follow-up.
The researchers used models adjusted for possible risk factors including the participants’ alcohol intake, menstrual cycle pattern in adolescence and physical activity. Additionally, researchers considered whether the risk of stroke could be influenced by other factors such as high blood pressure, having a hysterectomy and postmenopausal hormone therapy.
Absolute risk of stroke remains low
Researchers found women with a history of endometriosis had a 34% greater risk of stroke than women without a history of endometriosis in models adjusted for potential confounding factors.
“This is important to note but not an exceptionally high increased risk,” cautioned Stacey Missmer, Sc.D., another author of the study and a professor of obstetrics, gynecology and reproductive biology at the Michigan State University College of Human Medicine, told MNT. “Also, the absolute risk for any individual in their lifetime for stroke still remains quite low.”
Researchers found the association between endometriosis and increased risk of stroke to be partially mediated by occurrences of hysterectomies (the removal of the uterus) or oophorectomies (removal of the ovaries).
“We were able to calculate that about 40% of it could be … caused by the high prevalence of hysterectomy, with and without oophorectomy, but that means that there’s an additional 60% that … can’t be attributed to that, that must have other factors in play,” Prof. Missmer explained.
The association was also partially mediated by postmenopausal hormone therapy, beginning menopause at 45 years old or earlier as well as having a history of hypertension or high cholesterol. No significant differences were seen in the relationship between endometriosis and stroke across multiple factors including age, body mass index or history of infertility.
For this study, most participants (93%) were white women. However, Prof. Farland explained to MNT that “we would expect the findings of our study to be generalizable to other racial and ethnic groups.”
Dr. Ken Sinervo, medical director for the Center for Endometriosis Care in Atlanta told MNT that endometriosis is too often “poorly managed by hysterectomy, which may be unnecessary in many cases.”
“The result is an increased risk of cardiovascular diseases, which could otherwise be largely avoided with proper use of Laparoscopic Excision,” Dr. Sinervo wrote, referring to the procedure where a surgeon makes small incisions in the patient’s lower abdomen. Through those, surgeons will insert a camera to look for endometriosis lesions which they remove using a laparoscope.
Prof. Missmer said she hopes this study will raise awareness among health practitioners and endometriosis patients about the risks of hysterectomies.
“As this evidence builds of a relationship between that particular surgery and other lifelong, increased risk factors, women need to be more aware that there can be these other impacts of having those surgeries and the clinicians who care for them need to also be aware of that as well,” she explained.
Additionally, Prof. Missmer stressed that it’s important for health practitioners and endometriosis patients to be cognizant that endometriosis can impact a woman’s cardiovascular and cerebrovascular health.
“It means that primary care physicians, not just gynecologists need to be … monitoring and paying attention to all of the symptoms and risk factors of a patient with endometriosis,” she added.