Nearly 1 in 6 patients with RA develop interstitial lung disease within 20 years
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More than 15% of patients with rheumatoid arthritis develop interstitial lung disease within 20 years, with the latter condition associated with shorter survival, according to data published in Arthritis Care & Research.
“Patients with RA commonly experience fatigue and arthralgias; consequently, they are less active than healthy adults,” Cynthia S. Crowson, PhD, of the Mayo Clinic, and colleagues wrote. “As a result, studies have reported that a large proportion (up to 90%) of patients with radiologic evidence of RA-associated interstitial lung disease (RA-ILD) do not report respiratory symptoms. Because of this high frequency of asymptomatic disease, particularly with mild or early-stage disease, the exact incidence and prevalence of RA-ILD remain unknown.
“Inconsistent definitions, compounded by selection, referral and, perhaps, misclassification biases have led to widely varying estimates across studies, with the incidence of RA-ILD ranging from 2% to 61%,” they added. “These same factors have also led to inconsistent and, not infrequently, opposing conclusions pertaining to the patient- and disease-related factors associated with incident RA-ILD. As such, the interpretability of the currently available literature is limited and thereby, the answers to many important questions surrounding RA-ILD remain elusive.”
To assess the incidence, risk factors and outcomes of RA-ILD, and examine the time trends within RA-ILD incidence and mortality, Crowson and colleagues analyzed data from the Rochester Epidemiology Project (REP), a medical records linkage system for residents of Olmsted County, Minnesota. For their study, the researchers included 645 adults from REP with incident RA between 1999 and 2014. These patients were followed until death, emigration from Olmsted County or April 30, 2019. Among them, 53% never smoked.
The researchers defined ILD as the presence of a radiologist-defined pattern consistent with the disease based on chest computed tomography (CT). In cases with no chest CT, the researchers instead based their definition the presence of chest X-ray abnormalities compatible with ILD, as well as a restrictive pattern on pulmonary function testing considered consistent with the disease. Potential risk factors included age, sex, smoking status, obesity, seropositivity, extra-articular manifestations (EAMs) and treatments.
Crowson and colleagues performed their survival analysis by matching patients with RA-ILD to those with RA but without ILD. In addition, they compared RA-ILD frequency of and mortality among those diagnosed between 1999 and 2014 to a cohort from 1955 to 1994.
According to the researchers, 22 patients demonstrated ILD prior to RA diagnosis, while 51 developed ILD during follow-up. The 20-year cumulative incidence of ILD related to RA was 15.3%. Ever-smoking (HR = 1.92; 95% CI, 1.09-3.41), age at RA onset (HR = 1.89 per 10-year increase; 95% CI, 1.52-2.34) and severe EAMs (HR = 2.29; 95% CI, 1.05-4.98) were associated with incident RA-ILD.
“One in six people with rheumatoid arthritis will develop interstitial lung disease,” Crowson told Healio. “Interstitial lung disease is and is associated with poor outcomes. People with rheumatoid arthritis are just as likely to get interstitial lung disease nowadays as they were several decades ago, despite newer treatments for rheumatoid arthritis including biologics.”
Patients with RA-ILD demonstrated higher mortality, compared with matched patients with RA but without ILD (HR = 2.42; 95% CI, 1.32-4.41). RA-ILD incidence was non-significantly lower for those diagnosed with RA between 1999 and 2014 than 1955-1994, but mortality did improve.
“The good news is that outcomes have improved for people with rheumatoid arthritis who have interstitial lung disease,” Crowson said. “They are living longer now than they did in the past. Clinicians should be on the lookout for CT changes consistent with interstitial lung disease in people with rheumatoid arthritis, particularly older people and smokers. These CT changes should not be overlooked as they increase the risk of death.”
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