Researchers suggest women with endometriosis - particularly younger women - may be at greater risk for heart disease.
The research was led by Fan Mu, who was a research assistant at Brigham and Women's Hospital and Harvard Medical School in Boston, MA, at the time of study.
Endometriosis is a condition in which the tissue that normally lines the uterus grows on the outside of the reproductive organ or other areas of the body, including the ovaries and the fallopian tubes.
In the US, it is estimated that at least 11% of women - or 6 million - aged 15-44 have endometriosis, with the condition most common among those in their 30s and 40s.
While painful menstrual cramps can be a sign of endometriosis, many girls and women are unaware of this, meaning the condition often goes undiagnosed.
Mu and colleagues set out to investigate whether women with endometriosis are at greater risk for heart disease - the leading cause of death for both men and women in the US.
Younger women at greatest risk
The team analyzed the health records of 116,430 women who were part of the Nurses' Health Study II. Through surgical examination, endometriosis was diagnosed in 11,903 women over 20 years of follow-up.
Fast facts about endometriosis
- Other than pain, symptoms of endometriosis include bleeding or spotting between periods, digestive problems and infertility
- The exact causes of endometriosis are unclear
- However, researchers believe it is most likely caused by the displacement of tissue that is shed during menstruation.
The researchers found that women with endometriosis were 1.91 times more likely to develop chest pain, or angina, 1.52 times more likely to have a heart attack and 1.35 times more likely to require surgery or stenting to open blocked arteries, compared with women free of endometriosis.
Furthermore, women under the age of 40 who had endometriosis were found to be at three times greater risk for all three conditions, compared with women of the same age group who did not have endometriosis.
The findings remained even after accounting for use of oral contraceptives, hormone replacement therapy and numerous other factors that may influence heart disease risk, according to the researchers.
They note that the large study size and length of follow-up strengthen the findings. However, they were unable to account for other hormonal treatments and note that including women with suspected endometriosis that was not confirmed with surgery had no effect on the results.
The team admits that surgical treatment for endometriosis - which can include removal of the uterus or ovaries - may partly explain the increased risks identified; surgically induced menopause may raise heart disease risk, and this greater risk may be stronger for women of a younger age group.
Still, Mu says the findings suggest that women with endometriosis should be aware they may be at greater risk for heart disease, especially when younger.
Senior study author Stacey Missmer, director of epidemiologic research in reproductive medicine at Brigham and Women's Hospital, adds:
"It is important for women with endometriosis - even young women - to adopt heart-healthy lifestyle habits, be screened by their doctors for heart disease, and be familiar with symptoms because heart disease remains the primary cause of death in women."
Medical News Today recently reported on a study suggesting women's heart health may be overlooked by doctors.