Incidence of rheumatic diseases during the COVID-19 pandemic in South Korea

Abstract

Background/aims: The recent coronavirus disease 2019 (COVID-19) pandemic has been associated with changes in the epidemiology of not only infectious diseases but also several non-infectious conditions. This study investigated changes in the recorded incidence of various rheumatic diseases during the COVID-19 pandemic.

Methods: The number of patients for each disease from January 2016 to December 2020 was obtained from the Korean Health Insurance Review and Assessment Service database. We compared the incidence of nine rheumatic diseases (seropositive rheumatoid arthritis, systemic lupus erythematosus [SLE], idiopathic inflammatory myositis [IIM], ankylosing spondylitis [AS], systemic sclerosis, Sjögren's syndrome, Behçet's disease [BD], polymyalgia rheumatica, and gout) and hypertensive diseases to control for changes in healthcare utilisation before and after the COVID-19 outbreak. The disease incidence before and after the COVID-19 outbreak was compared using the autoregressive integrated moving average (ARIMA) and quasi- Poisson analyses.

Results: Compared with the predicted incidence in 2020 using the ARIMA model, the monthly incidence of SLE, BD, AS, and gout temporarily significantly decreased, whereas other rheumatic diseases and hypertensive diseases were within the 95% confidence interval (CI) of the predicted values in the first half of 2020. In age- and sex-adjusted quasi-Poisson regression analysis, the annual incidences of IIM (rate ratio [RR], 0.473; 95% CI, 0.307 to 0.697), SLE (RR, 0.845; 95% CI, 0.798 to 0.895), and BD (RR, 0.850; 95% CI, 0.796 to 0.906) were significantly decreased compared with those in the previous 4 years.

Conclusion: The recorded annual incidence of some rheumatic diseases, including IIM, SLE, and BD, decreased during the COVID-19 pandemic.

Keywords: COVID-19; Epidemiology; Incidence; Rheumatic diseases.

Figure 1

The monthly incidence and predicted incidence of (A) systemic lupus erythematosus, (B) Behçet’s disease, (C) ankylosing spondylitis, (D) Sjögren’s syndrome, (E) idiopathic inflammatory myositis, (F) rheumatoid arthritis, (G) systemic sclerosis, (H) polymyalgia rheumatica, (I) gout, and (J) hypertensive diseases using the autoregressive integrated moving average (ARIMA) model. The blue line denotes the monthly predicted incidence for 2020 using the ARIMA model. Blue and grey shades denote the 80% and 95% confidence intervals of the predicted incidence.

Figure 2

The annual incidence of various diseases in 2020 versus 2016–2019. CI, confidence interval; IIM, idiopathic inflammatory myositis; SLE, systemic lupus erythematosus; BD, Behçet’s disease; SjS, Sjögren’s syndrome; AS, ankylosing spondylitis; SSc, systemic sclerosis; RA, rheumatoid arthritis; PMR, polymyalgia rheumatica; HTN, hypertensive diseases.