medwireNews: Interstitial lung disease (ILD) affects a substantial proportion of patients with rheumatoid arthritis (RA) and is associated with reduced survival, but the condition is overlooked by clinicians, suggest results from a population-based study.
For the study, Cynthia Crowson (Mayo Clinic, Rochester, Minnesota, USA) and colleagues analyzed data from 645 adults (median age 55.3 years, 70% women) with incident RA identified in 1999–2014 who were followed up until death, emigration, or 2019. Of these, 22 had ILD before RA diagnosis and 51 developed ILD during follow-up, at a median age of 73.7 years.
Grouping all patients with ILD (n=73), the authors report a cumulative ILD incidence of 7.6%, 11.0%, 12.4%, and 15.3% at 5, 10, 15, and 20 years after RA onset, respectively.
The team then matched each of the 51 patients who developed ILD after RA diagnosis to two comparators with RA and no ILD (n=102), with median follow-up periods of 3.5 years and 4.8 years, respectively. On multivariable analysis, the presence of ILD was significantly associated with an increased risk for death (hazard ratio [HR]=2.42), as was older age (HR=2.92 per 10-year increase).
Writing in Arthritis Care & Research, Crowson et al remark that “[d]espite its association with more than double the risk of death,” ILD “is commonly overlooked by clinicians.” Indeed, they only saw documentation of ILD in the medical records of 27% (n=14) of the 51 patients with incident RA-ILD.
In light of “the prognostic and therapeutic implications of detecting RA-ILD in its early stages,” the authors highlight the importance of identifying people at risk.
To address this, they evaluated risk factors for incident RA-ILD, finding that ever-smoking, age at RA onset, and severe extra-articular manifestations were significantly associated with RA-ILD risk, at adjusted hazard ratios (HRs) of 1.92, 1.89 (per 10-year increase), and 2.29, respectively.
The investigators also looked at time trends in the incidence and survival of RA-ILD by comparing 603 patients diagnosed with RA during 1955–1994 with 645 diagnosed during 1999–2014. They observed that the cumulative 20-year incidence of RA-ILD was not significantly lower in 1999–2014 versus 1955–1994 (6.3 vs 4.2%). However, survival did significantly improve, from a median of 2.6 years in the first period to 11.2 years in the second, with an HR of 0.41.
This finding, they say, “is noteworthy and deserves further exploration.”
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