Patients with rheumatoid arthritis–associated interstitial lung disease showed increases in overall mortality, respiratory mortality, and cancer mortality, compared with RA patients without interstitial lung disease, based on data from more than 500,000 patients in a nationwide cohort study.
RA-associated interstitial lung disease (RA-ILD) has been associated with worse survival rates as well as reduced quality of life, functional impairment, and increased health care use and costs, wrote Jeffrey A. Sparks, MD, of Brigham and Women’s Hospital, Boston, and colleagues. However, data on the incidence and prevalence of RA-ILD have been inconsistent and large studies are lacking.
In a study published online in Rheumatology, the researchers identified 509,787 RA patients aged 65 years and older from Medicare claims data. The average age of the patients was 72.6 years, and 76.2% were women.
At baseline, 10,306 (2%) of the study population had RA-ILD, and 13,372 (2.7%) developed RA-ILD over an average of 3.8 years’ follow-up per person (total of 1,873,127 person-years of follow-up). The overall incidence of RA-ILD was 7.14 per 1,000 person-years.
Overall mortality was significantly higher among RA-ILD patients than in those with RA alone in a multivariate analysis (38.7% vs. 20.7%; hazard ratio, 1.66).
In addition, RA-ILD was associated with an increased risk of respiratory mortality (HR, 4.39) and cancer mortality (HR, 1.56), compared with RA without ILD. For these hazard regression analyses, the researchers used Fine and Gray subdistribution HRs “to handle competing risks of alternative causes of mortality. For example, the risk of respiratory mortality for patients with RA-ILD, compared with RA without ILD also accounted for the competing risk of cardiovascular, cancer, infection and other types of mortality.”
In another multivariate analysis, male gender, smoking, asthma, chronic obstructive pulmonary disorder, and medication use (specifically biologic disease-modifying antirheumatic drugs, targeted synthetic DMARDs, and glucocorticoids) were independently associated with increased incident RA-ILD at baseline. However, “the associations of RA-related medications with incident RA-ILD risk should be interpreted with caution since they may be explained by unmeasured factors, including RA disease activity, severity, comorbidities, and prior or concomitant medication use,” the researchers noted.
The study findings were limited by several factors, including the lack of data on disease activity, disease duration, disease severity, and RA-related autoantibodies, the researchers noted. However, the results support data from previous studies and were strengthened by the large sample size and data on demographics and health care use.
“Ours is the first to study the epidemiology and mortality outcomes of RA-ILD using a validated claims algorithm to identify RA and RA-ILD,” and “to quantify the mortality burden of RA-ILD and to identify a potentially novel association of RA-ILD with cancer mortality,” they noted.
The study was supported by an investigator-initiated grant from Bristol-Myers Squibb. Lead author Sparks disclosed support from the National Institute of Arthritis and Musculoskeletal and Skin Diseases, the Rheumatology Research Foundation, the Brigham Research Institute, and the R. Bruce and Joan M. Mickey Research Scholar Fund. Sparks also disclosed serving as a consultant to Bristol-Myers Squibb, Gilead, Inova Diagnostics, Janssen, Optum, and Pfizer for work unrelated to the current study. Other authors reported research funding from Bristol-Myers Squibb, involvement in a clinical trial funded by Genentech and Bristol-Myers Squibb, and receiving research support to Brigham and Women’s Hospital for other studies from AbbVie, Bayer, Bristol-Myers Squibb, Novartis, Pfizer, Roche, and Vertex.