Shielding reduced incidence of COVID-19 in patients with inflammatory arthritis but vulnerability is associated with increased mortality

OBJECTIVES: Investigate whether individuals with inflammatory arthritis (IA), their treatments and shielding status affect the risk of adverse outcomes from COVID-19 for the entire population of Wales, UK. METHODS: Retrospective, population-based cohort study using linked, anonymized electronic health data from SAIL Databank, including primary/secondary care, rheumatology, Office for National Statistics Mortality and COVID-19 laboratory data. Individuals aged 18 years and over testing positive for COVID-19 between March 2020 and May 2021 with READ Codes present for rheumatoid arthritis, psoriatic arthritis and ankylosing spondylitis formed the study cases. RESULTS: A total of 1966 people with IA and 166 602 without tested positive for COVID-19. The incidence rate was 3.5% (1966/56 914) in IA, vs 6% in the general population (166 602/2 760 442), (difference: 2.5%, 95% CI: 2.4%, 2.7%, P ≤0.001). In an adjusted Cox proportional hazard model, IA was not associated with higher mortality (HR: 0.56, 95% CI: 0.18, 1.64, P=0.286). Significant risk factors included shielding (HR: 1.52, 95% CI: 1.40, 1.64, P ≤0.001), hospitalization for previous infections (HR: 1.20, 95% CI: 1.12, 1.28, P ≤0.001), hospitalizations one year pre-pandemic (HR: 1.34, 95% CI: 1.25, 1.44, P ≤0.001) and glucocorticoid use (HR: 1.17, 95% CI: 1.09, 1.25, P ≤0.001). CONCLUSIONS: Individuals with IA had a lower incidence of COVID-19, probably due to shielding. IA was not associated with increased mortality following COVID-19 infection; being vulnerable (shielded), comorbidities and other factors were associated with increased risk. These key risk factors can identify individuals with IA at greater risk from COVID-19 and advised to shield during high community prevalence.