Comorbidity clusters in patients with rheumatoid arthritis identify a patient phenotype with a favourable prognosis.

OBJECTIVES: We aimed to cluster patients with rheumatoid arthritis (RA) based on comorbidities and then examine the association between these clusters and RA disease activity and mortality. METHODS: In this population-based study, residents of an eight-county region with prevalent RA on 1 January 2015 were identified. Patients were followed for vital status until death, last contact or 31 December 2021. Diagnostic codes for 5 years before the prevalence date were used to define 55 comorbidities. Latent class analysis was used to cluster patients based on comorbidity patterns. Standardised mortality ratios were used to assess mortality. RESULTS: A total of 1643 patients with prevalent RA (72% female; 94% white; median age 64 years, median RA duration 7 years) were studied. Four clusters were identified. Cluster 1 (n=686) included patients with few comorbidities, and cluster 4 (n=134) included older patients with 10 or more comorbidities. Cluster 2 (n=200) included patients with five or more comorbidities and high prevalences of depression and obesity, while cluster 3 (n=623) included the remainder. RA disease activity and survival differed across the clusters, with cluster 1 demonstrating more remission and mortality comparable to the general population. CONCLUSIONS: More than 40% of patients with prevalent RA did not experience worse mortality than their peers without RA. The cluster with the worst prognosis (<10% of patients with prevalent RA) was older, had more comorbidities and had less disease-modifying antirheumatic drug and biological use compared with the other clusters. Comorbidity patterns may hold the key to moving beyond a one-size-fits-all perspective of RA prognosis.

Multiple morbidities are associated with serious infections in patients with rheumatoid arthritis.

OBJECTIVE: To assess the association between a comprehensive list of morbidities and serious infection (SI) in patients with rheumatoid arthritis (RA). METHODS: This study evaluated SI risk associated with 55 comorbidities using a population-based inception cohort including all adult patients with incident RA from 1999 through 2014 with follow up through 2021. Morbidities and SI were ascertained using previously validated international classification of disease (ICD)-9 and ICD-10 codes. Conditional frailty models were utilized to analyze the association between each morbidity and SI: Model 1 adjusted for age, sex, and calendar year; Model 2 adjusted for factors in Model 1 and the Rheumatoid Arthritis Observation of Biologic Therapy (RABBIT) Risk Score of Infections; and Model 3 adjusted for factors in Model 1 and the Mayo SI Risk Score. RESULTS: 911 patients (70 % female, mean age 56 years, 66 % seropositive) were included. There were 293 SI among 155 patients (17 %), corresponding to an incidence of 3.9 SI per 100 person-years. Eighteen SI were fatal. Risk of SI was significantly increased in 27 of 55 morbidities in Model 1, 11 morbidities in Model 2, and 23 morbidities in Model 3. Additionally, several morbidities included in the RABBIT and Mayo risk scores continued to have large effect sizes despite adjustment. Serious infection risk increased by 11-16 % per morbidity in the three models. CONCLUSIONS: Several morbidities are associated with an increased risk for SI. Future risk scores may include morbidities identified in this study for improved SI risk assessment.