Impact of the COVID-19 pandemic on morbidity and mortality in patients with inflammatory joint diseases and in the general population: a nationwide Swedish cohort study

Abstract

Objectives: To estimate absolute and relative risks for all-cause mortality and for severe COVID-19 in inflammatory joint diseases (IJDs) and with antirheumatic therapies.

Methods: Through Swedish nationwide multiregister linkages, we selected all adult patients with rheumatoid arthritis (RA, n=53 455 in March 2020), other IJDs (here: spondyloarthropathies, psoriatic arthritis and juvenile idiopathic arthritis, n=57 112), their antirheumatic drug use, and individually matched population referents. We compared annual all-cause mortality March-September 2015 through 2020 within and across cohorts, and assessed absolute and relative risks for hospitalisation, admission to intensive care and death due to COVID-19 March-September 2020, using Cox regression.

Results: During March-September 2020, the absolute all-cause mortality in RA and in other IJDs was higher than 2015-2019, but relative risks versus the general population (around 2 and 1.5) remained similar during 2020 compared with 2015-2019. Among patients with IJD, the risks of hospitalisation (0.5% vs 0.3% in their population referents), admission to intensive care (0.04% vs 0.03%) and death (0.10% vs 0.07%) due to COVID-19 were low. Antirheumatic drugs were not associated with increased risk of serious COVID-19 outcomes, although for certain drugs, precision was limited.

Conclusions: Risks of severe COVID-19-related outcomes were increased among patients with IJDs, but risk increases were also seen for non-COVID-19 morbidity. Overall absolute and excess risks are low and the level of risk increases are largely proportionate to those in the general population, and explained by comorbidities. With possible exceptions, antirheumatic drugs do not have a major impact on these risks.

Keywords: Covid-19; arthritis; biological therapy; epidemiology; health care; outcome assessment; rheumatoid.

Figure 1

All-cause mortality in adult Swedish residents with rheumatoid arthritis (RA) or other inflammatory joint diseases (IJDs, defined as ankylosing spondylitis, psoriatic arthritis, other spondyloarthropathies and juvenile idiopathic arthritis), and among individually matched general population subjects, during 1 March until September 2020 compared with the corresponding average mortality during the same seasons 2015 through 2019.

Figure 2

Difference (excess or deficit) in all-cause mortality for Swedish residents with rheumatoid arthritis (RA), other inflammatory joint diseases (IJDs, defined as ankylosing spondylitis, psoriatic arthritis, other spondyloarthropathies and juvenile idiopathic arthritis) and in their individually matched general population cohorts 1 March until September 2020, estimated as the difference between the mortality in each cohort 2020 compared with the average mortality in the same cohort during the same seasons 2015 through 2019.