Incidence and disease burden of autoimmune inflammatory rheumatic diseases after non-pharmaceutical interventions in the COVID-19 era: A nationwide observational study in Korea.

Background: Infections are considered risk factors for autoimmune inflammatory rheumatic diseases (AIRDs), the incidence of which is considered to have been impacted by the COVID-19 pandemic. The impact of non-pharmaceutical interventions (NPIs) on the incidence of AIRDs and their associated health care services and medical expenses in Korea was investigated.

Methods: We included all AIRD cases reported between January 2016 and February 2021 based on the National Health Insurance Service data. We evaluated changes in incidence trends for each AIRD before and after NPI implementation (Feb 2020 to Feb 2021) using segmented regression analysis. Changes in health care utilization and medical costs for each AIRD before and after NPI implementation were also investigated.

Results: After NPI implementation, monthly incidence rates declined significantly by 0.205 per 1 000 000 (95% confidence interval [CI], -0.308 to -0.101, p < .001) in patients with systemic lupus erythematosus (SLE). No significant changes in the incidence of all AIRDs other than SLE were observed before and after implementation. Further, annual outpatient department visits per patient were lower during implementation for all diseases, except juvenile idiopathic arthritis (JIA). The prescription days per outpatient visit increased significantly during implementation for all diseases, except JIA and ankylosing spondylitis. During implementation, the total annual medical costs per patient tended to decrease for all diseases, except JIA and mixed connective tissue disease.

Conclusion: Implementation of NPIs to contain the pandemic led to a reduction in the incidence of SLE and changed patterns of medical care utilization and treatment cost for most AIRDs.