Association between Graves' disease and risk of incident systemic lupus erythematosus: A nationwide population-based cohort study

Objective Previous case reports have linked Graves' disease to incident systemic lupus erythematosus (SLE). It has also been reported that antithyroid drugs used to treat Graves' disease can induce SLE development. The purpose of this study was to investigate the risk of SLE in patients with Graves' disease. Methods A total of 8779 patients with Graves' disease and 8779 controls (without Graves' disease) matched by age, gender, index year, and Charlson Comorbidity Index (CCI) score were enrolled between 2000-2012. 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 Graves' disease and unaffected controls. Results Patients with Graves' disease had a significantly increased risk of SLE than unaffected controls (8.81 vs 2.83 per 10 000 person-years, HR: 5.45, 95% CI: 1.74-17.0) after adjusting for antithyroid therapies (antithyroid drugs, radioactive iodine ablation, and surgery). Diagnostic bias may be present as patients with Graves' disease may seek more help from healthcare providers. After excluding the first 0.5 and 1 year of observation period, similar results were obtained (excluding 0.5 year - HR: 4.30, 95% CI: 2.78-8.57; excluding 1 year - HR: 4.63, 95% CI: 2.33-7.79). Conclusion This study shows that Graves' disease is associated with an increased risk of incident SLE. Further studies on the underlying pathogenesis linking Graves' disease and SLE are warranted.