The incidence of interstitial lung disease (ILD) in rheumatoid arthritis (RA) has not significantly changed in the last 6 decades, but survival rates have improved, according to study findings published in Arthritis Care & Research.
Patients aged 18 years and older living in Olmstead County, Minnesota between 1999 and 2014 who fulfilled the American College of Rheumatology (ACR) classification criteria were included in the retrospective population-based cohort study.
Researchers used Rochester Epidemiology Project (REP) medical records to search for current procedural terminology (CPT) codes indicative of chest computed tomography (CT) imaging and chest CT scan reports. The presence of ILD was defined as bilateral interstitial fibrotic changes (excluding apical scarring) or a pattern that was highly consistent with ILD. Remaining records without CT codes were searched for International Classification of Diseases, Ninth Revision (ICD-9) and ICD, Tenth Revision (ICD-10) diagnostic codes suggestive of ILD. Patients were followed-up with until death, emigration, or April 30, 2019, whichever came first.
A total of 645 individuals (70% women) with incident RA were included in the study. Among patients with RA with no prior ILD, 8% (n=51) developed ILD during follow-up, which was supported by consistent CT imaging in all patients. Overall, 27% of these patients (n=14/51) with incident RA-ILD had documentation of ILD in their clinical notes.
Risk factors included age (adjusted hazard ratio [aHR], 1.89 for each 10-year increment; 95% CI, 1.52-2.34), ever-smoking status at RA onset (aHR, 1.92; 95% CI, 1.09-3.41), and the presence of severe extra-articular manifestations (aHR, 2.29; 95% CI, 1.05-4.98). A comparison of the mortality in patients with RA-ILD with those with RA without ILD showed no difference in age or duration of RA incidence (67.5 and 66.5 years, respectively). Multivariable Cox models that included age, presence or absence of ILD, and age at ILD diagnosis or index date showed that advanced age (hazard ratio [HR], 2.92 for every 10-year increment; 95% CI, 2.06-4.14) and age at ILD diagnosis/index date (HR, 2.42; 95% CI, 1.32-4.41) were associated with shorter survival.
Limitations of this study included its retrospective design that relied on what could be ascertained from medical records and that the Disease Activity Score (DAS28) was not documented, because of which overall survival was assessed without characterizing the clinical or radiologic course in patients with RA-ILD. According to the researchers, the small number of RA-ILD events may have hindered the ability to reach statistical significance, and the results of the study may have been limited in generalizability due to the mostly homogenous population in Olmstead County, Minnesota.
Researchers indicated that, despite the association between RA and ILD, which can mean twice the risk for death, the changes on CT consistent with ILD is commonly overlooked by clinicians.
“Ever-smoking and older age at RA onset, along with certain [extra-articular manifestations] are predictive of incident ILD,” the researchers advised. “Over the past  decades, the survival associated with clinician-diagnosed RA-ILD has improved, but its incidence has not significantly decreased. This finding is noteworthy and deserves further exploration.”
Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.
Samhouri BF, Vassallo R, Achenbach SJ, et al. The incidence, risk factors, and mortality of clinical and subclinical rheumatoid arthritis-associated interstitial lung disease: a population-based cohort. Arthritis Care Res (Hoboken). Published online January 7, 2022. doi:10.1002/acr.24856