Patients with endometriosis are at increased risk of developing rheumatoid arthritis (RA), according to study results published in Rheumatology.

Previous studies have suggested similarities between endometriosis and several autoimmune diseases, including high levels of cytokines, decreased apoptosis, and cell-mediated abnormalities.

The objective of the current nationwide population-based cohort study was to determine the association between endometriosis and risk for RA.

Using data from the Longitudinal Health Insurance Database 2000 from Taiwan, the incidence of RA among women with endometriosis was determined. Propensity scores were used to match women with endometriosis with those without endometriosis.


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The study sample included 14,463 women in the endometriosis group (mean age, 38.7 years) and the group without endometriosis (mean age, 38.9 years) who were propensity score-matched by age, comorbidities, corticosteroids, nonsteroidal anti-inflammatory drugs (NSAIDs), and hormonal medications.

The cumulative incidence of RA was significantly higher in the endometriosis group compared with the group without endometriosis (0.9 vs 0.5 cases per 1000 person-years, respectively; P =.001). The risk for RA was significantly increased among women with endometriosis (adjusted hazard ratio [HR], 1.75; 95% CI, 1.27-2.41), those aged 45 years or greater (adjusted HR, 1.50; 95% CI, 1.06-2.13) and those with autoimmune disease (adjusted HR, 6.99; 95% CI, 2.84-17.21).

A diagnosis of endometriosis was associated with increased risk for RA in patients aged 20 to 45 years (HR, 1.85; 95% CI, 1.24-2.74) and in those with and without use of hormonal medications (HR, 1.76; 95% CI, 1.12-2.76 and HR, 1.73; 95% CI, 1.10-2.72, respectively).

In addition, the risk for RA in patients with endometriosis, when stratified by age, comorbidities, as well as use of corticosteroids and NSAIDs, was higher compared with patients without endometriosis.

The study had several limitations, including the challenges associated with the diagnosis of endometriosis, potential bias, and that not all symptomatic patients seek medical consultation.

“This 14-year, nationwide, population-based retrospective cohort study revealed that patients with endometriosis have a higher risk [for] RA. In the clinical management of patients with RA, rheumatologists should be especially mindful of the possibility of underlying endometriosis,” the researchers concluded.

Reference

Xue Y-H, You L-T, Ting H-F, et al. Increased risk of rheumatoid arthritis among patients with endometriosis: a nationwide population-based cohort study. Rheumatology (Oxford). Published online December 17, 2020. doi:10.1093/rheumatology/keaa784