Background: Interstitial lung disease (ILD) is a common extra-articular manifestation of RA and is associated with increased morbidity and mortality.1-3 Studies have shown variability in the prevalence and mortality rate of patients with RA-associated ILD (RA-ILD).4 Further studies are needed to better characterise the epidemiology of RA-ILD.
Objectives: To estimate the prevalence and incidence of clinical RA-ILD in France and to compare mortality rates between patients with RA-ILD and patients with RA without clinical ILD (RA-noILD).
Methods: A historical cohort study was conducted using data from the French national claims database (SNDS) between 1 January 2013 and 31 December 2018. Adults with an RA diagnosis (International Classification of Diseases, Tenth revision [ICD-10] codes M05, M06.0, M06.8 and M06.9) and ≥2 distinct dates of DMARD delivery were included. Onset of RA was defined as the first date of occurrence between RA codes and the first known DMARD reimbursement. ILD diagnosis was defined as having ICD-10 code J84 and ≥1 computed tomography scan after, but within 1 year of, the first date of ILD occurrence. All patients had ≥6 months’ reimbursement after RA-ILD onset. The prevalence and incidence (2014–2018) of RA-ILD were estimated. The mortality rate was calculated, comparing patients with RA-ILD and patients with RA-noILD, matched 1:1 for age, sex, age at RA-ILD onset, duration of RA and presence of diabetes, arterial disease, dyslipidaemia and cardiac disease. Mortality was compared between patients with RA with and without clinical ILD in the matched population using Cox proportional hazards regression.
Results: The prevalence of RA-ILD was 6.52 per 100,000 inhabitants (incidence=1.04 per 100,000 person-years). Of the 173,138 patients with RA included in the overall population, 4330 (2.5%) had clinical ILD. Patients with RA-ILD were older at RA diagnosis (mean [SD] age: 63.3 [13.7] vs 56.9 [15.2] years) and were more likely to be male (39.8% vs 27.0%) compared with patients with RA-noILD. Patients with RA-ILD were more likely to have cardiac disease (84.9% vs 63.1%), arterial disease (38.0% vs 19.3%), diabetes (21.4% vs 12.5%) and dyslipidaemia (44.7% vs 32.9%) compared with those with RA-noILD. The mortality rate in patients with clinical RA-ILD was 1.71 per 100,000 inhabitants. The mortality rate increased according to age (0.28 per 100,000 inhabitants for patients aged <65 years, 4.60 per 100,000 inhabitants for patients aged 65–74 years and 11.4 per 100,000 inhabitants for patients aged ≥75 years). After matching, the adjusted mortality risk was three times higher (HR [95% CI]: 3.1 [3.1, 3.9]) in patients with RA-ILD than in those with RA-noILD (Figure 1).
Conclusion: This is the largest epidemiological study of RA-ILD in France. The prevalence of clinical RA-ILD in this population was towards the lower end of previous estimates (1–58%),3 possibly due to under-reporting of claims data. However, the occurrence of clinical ILD was associated with a strong increase in mortality compared with patients with RA-noILD.
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Acknowledgements: This study was funded by Bristol Myers Squibb. Claire Line, PhD of Caudex provided medical writing support, funded by Bristol Myers Squibb.
Disclosure of Interests: Pierre-Antoine Juge Consultant of: Bristol Myers Squibb, Lidwine Wemeau Stervinou Consultant of: Boehringer Ingelheim, Bristol Myers Squibb, Roche, Sanofi, Sebastien Ottaviani Consultant of: AbbVie, Bristol Myers Squibb, Lilly, Merck Sharp & Dohme, Novartis, Roche-Chugai, SOBI, UCB, Guillaume Desjeux: None declared, Joe Zhuo Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, Bruno Bregman Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, Virginie Vannier-Moreau Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, Rene-Marc Flipo Speakers bureau: AbbVie, Bristol Myers Squibb, Janssen, Lilly, Medac, Merck Sharp & Dohme, Novartis, Pfizer, Roche-Chugai, Grant/research support from: Amgen, Janssen, Novartis, Pfizer, Bruno Crestani: None declared, Philippe Dieudé Consultant of: Boehringer Ingelheim, Bristol Myers Squibb, Chugaï, Lilly, Medac, Novartis, Pfizer, Sanofi, Grant/research support from: Bristol Myers Squibb, GlaxoSmithKline, Pfizer
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