Multimorbidity Burden in Rheumatoid Arthritis: A Population-based Cohort Study

Area of Science:

• Rheumatology
• Epidemiology
• Public Health

Background:

• Rheumatoid arthritis (RA) is a chronic inflammatory disease.
• Multimorbidity (MM), the coexistence of two or more chronic conditions, poses a significant health burden.
• Understanding MM prevalence and incidence in RA is crucial for patient care and resource allocation.

Purpose of the Study:

• To estimate the prevalence and incidence of multimorbidity (MM) in a population-based cohort of patients with rheumatoid arthritis (RA).
• To compare MM rates in RA patients versus subjects without RA.
• To analyze the development of MM over time following RA diagnosis.

Main Methods:

• A population-based cohort study comparing RA patients (n=597) meeting 1987 ACR criteria with age- and sex-matched non-RA subjects (n=594) from 1999-2013.
• Inclusion of 25 chronic comorbidities (excluding rheumatic ones) using Charlson, Elixhauser, and Rheumatic Disease Comorbidity Indices.
• Application of the Aalen-Johansen method to estimate cumulative incidence of MM (≥2 comorbidities) and substantial MM (≥5 comorbidities), adjusting for competing risks of death.

Main Results:

• At RA incidence/index, MM prevalence (≥2 comorbidities) was higher in RA patients (38%) than non-RA subjects (32%; P=0.02).
• During follow-up (median ~11.5 years), RA patients had a higher incidence of MM (adjusted HR 1.39; 95% CI 1.14-1.69).
• Cumulative incidence of MM (≥2 comorbidities) by 10 years was 56.5% in RA patients vs. 47.9% in non-RA subjects; incidence of MM (≥5 comorbidities) was similar between groups.

Conclusions:

• Patients with rheumatoid arthritis exhibit a higher prevalence of multimorbidity at the time of RA diagnosis.
• RA patients experience an increased incidence of multimorbidity following their diagnosis.
• These findings underscore the heightened burden of multiple chronic conditions in individuals with RA.