Endometriosis was associated with an approximately 50% greater long-term risk of venous thromboembolism (VTE), including higher risks of deep venous thrombosis (DVT) and pulmonary embolism (PE), compared with no endometriosis, according to research published Aug. 8 in the EHJ.

In this nationwide, registry-based cohort study, Helene Vistisen Ryde, MD, et al., matched all women in Denmark with a diagnosis of endometriosis from 1977 to 2024 (n=63,999) 1:4 by birth year and year of diagnosis with women without endometriosis (n=255,996). At baseline, women with endometriosis had a higher burden of comorbidities, greater medication use and more abdominal/gynecological surgeries.

During a median follow-up of 18.2 years and maximum follow-up of 47 years, VTE occurred in 4.2% of women with endometriosis and 3.1% of controls. The 40-year cumulative incidence of VTE was 10.7% vs. 8.3%, corresponding to incidence rates of 2.18 vs. 1.54 per 1,000 person-years (hazard ratio [HR], 1.43). The association persisted after adjustment for relevant comorbidities and hormonal contraception use (adjusted HR [aHR], 1.52), as well as across multiple sensitivity analyses and decades of follow-up.

The pattern was similar for DVT (1.48 vs. 1.02 per 1,000 person-years; aHR, 1.50) and PE (0.89 vs. 0.65 per 1,000 person-years; aHR, 1.52). All-cause mortality was comparable between groups (aHR, 1.04).

"The observed association between endometriosis and VTE may be biologically plausible considering the chronic systemic inflammation associated with endometriosis and its treatment modalities. Inflammation in endometriosis can upregulate pro-coagulant factors and increase platelet reactivity, favoring thromboembolic events," write the authors.

Although the findings "do not justify universal screening or routine primary thromboprophylaxis," they add that "the results contribute to the growing recognition of endometriosis as a potential female-specific cardiovascular risk factor and highlight the need for improved risk stratification."