Risk of systemic lupus erythematosus in patients with endometriosis: A nationwide population-based cohort study

The etiology of endometriosis is mostly under-explored, but abnormalities in the immune system leading to an autoimmune reaction have been suggested. The systemic lupus erythematosus (SLE) is one of the most common autoimmune diseases. The purpose of this study was to investigate the risk of SLE in patients with endometriosis. A total of 17,779 patients with endometriosis and 17,779 controls (without endometriosis) matched by age, index year, and Charlson Comorbidity Index (CCI) score were enrolled between 2000 and 2012. Patients were then followed until the end of 2013 using Taiwan’s National Health Insurance Research Database, at which time participants who developed SLE were identified. Cox regression analysis was used to calculate the hazard ratio (HR) with a 95% confidence interval (CI) of SLE incidence rate between patients with endometriosis and unaffected controls. After adjusting for age, CCI score, and different treatment options, patients with endometriosis were at increased risk of SLE compared to unaffected controls (0.85 versus 0.57 per 1000 person-years, HR 1.86, 95% CI 1.36–2.53). Also, higher baseline CCI scores (CCI score 1–2 and ≥ 3 vs. 0—HR 2.33–4.98) were at increased risk of SLE. During follow-up, hormonal treatment for endometriosis could reduce the risk of SLE (short-term and long-term vs. non-use HR 0.48–0.62), while surgical treatment appeared to have a limited impact on the risk of SLE. Patients with endometriosis were at increased risk of SLE, and adequate hormonal treatment could reduce the risk of SLE, providing a reference for developing prevention interventions.