0168: Risk of hospitalization in patients with rheumatoid arthritis-associated interstitial lung disease or bronchiectasis: A matched cohort study

Background/Purpose: RA-associated lung disease (RA-LD), including RA-associated interstitial lung disease (RA-ILD) and RA-associated bronchiectasis (RA-BR), is a serious extra-articular manifestation of RA that significantly contributes to morbidity and mortality. Although previous studies have documented the adverse clinical outcomes associated with RA-LD, its impact on hospitalization risk is insufficiently investigated, particularly for RA-BR.

Methods: We conducted a retrospective matched cohort study of patients enrolled in the biobank of a large U.S. health care system, comparing RA-LD cases to RA comparators without lung disease (RA-no LD), matched by calendar date, age, sex, and RA duration at the index date. The index date was defined as the later date of the RA or ILD/BR diagnosis for RA-LD cases, and the matched date for RA-no LD comparators. Patients with RA met the 2010 ACR/EULAR classification criteria. RA-LD cases were verified by medical record review and chest imaging for clinically-apparent RA-ILD and/or RA-BR. The primary outcomes were overall and respiratory hospitalizations. Secondary outcomes included emergency department (ED) visits and intensive care unit (ICU) admissions. Incidence rates were calculated per 100 person-years. Incidence rate ratios (IRRs) with 95% confidence intervals (CI) were estimated using multivariable Poisson regression models, comparing RA-LD cases vs. RA-no LD comparators as well as for RA-ILD and RA-BR cases vs. RA-no LD comparators, with adjustment for the propensity score as a covariate.

Results: We analyzed 221 RA-LD cases (151 RA-ILD and 70 RA-BR) and 980 matched RA-no LD comparators (Table 1). RA-LD patients had higher rates of overall hospitalization (60% vs. 41%, p< 0.001) and respiratory hospitalization (23% vs. 6%, p< 0.001), along with higher proportions of ED visits (57% vs. 48%, p=0.02) and ICU admissions (36% vs. 20%, p< 0.001, Table 2). RA-LD patients had a shorter time from the index date to first hospitalization (median 922 vs. 1,217 days, p=0.01) compared to RA-no LD comparators. They also had a shorter time to first respiratory hospitalization (median 1,588 vs. 2,253 days, p=0.009), including RA-ILD (median 1,707 vs. 2,253 days, p=0.03) and RA-BR (median 1,436 vs. 2,253 days, p=0.04). RA-LD, including RA-ILD and particularly RA-BR, had higher risks of overall hospitalization (adjusted IRR 1.73, 95%CI 1.57-1.91) and respiratory hospitalization (adjusted IRR 5.13, 95%CI 3.80-6.94, Table 3). RA-ILD was associated with an increased risk of ICU admissions (adjusted IRR 1.99, 95%CI 1.81-2.18).

Conclusion: RA-LD was associated with higher risks of overall hospitalization, respiratory hospitalization, and ICU admissions than RA-no LD comparators. RA-BR had a similarly elevated hospitalization risk as RA-ILD, illustrating an unreported unmet need in this population. These findings highlight the need for targeted strategies to prevent and manage acute care utilization in RA patients with lung involvement.