Prevalence and incidence of interstitial lung diseases (ILDs) in a French multi-ethnic county

Rationale: Publications on the epidemiology of ILDs are rare and often encompass major methodology limitations. The aim of our study was to assess comprehensively the global and relative prevalence and incidence of ILDs in adults living in Seine Saint Denis. Methods: Patients with an incident or prevalent ILD during the study period (from 11/2011 to 11/2012) were recruited using three different sources: 1) Hospital departments of pneumology, internal medicine, rheumatology, occupational disease and geriatrics from the county and neighboring areas 2) General practitioners and community chest physicians 3) National Public Health Insurance System (NHIS) database. Each identified case was centrally reviewed by an expert panel. Result: Current results do not account for the NHIS records. 576 prevalent and 190 incident cases have been declared (age: 60.6±15.6 years-old, female/male: 1.18). The diagnosis could be determined in 90% of cases according to most recent international guidelines. 78 cases have not yet been reviewed. Overall prevalence and incidence were 48.8/100000 and 16.1/100000/year, respectively. For prevalent cases with determined diagnosis, sarcoidosis was the most frequent (44%; 20/100000), followed by ILDs of known cause (30%; 13.3/100000) and IIPs (15%; 6.8/100000). The prevalence of IPF was 4.1/100000 and that of NSIP was 1.3/100000. It reached 6.2/100000 when cases with IPF, NSIP and undetermined diagnosis between IPF and NSIP were gathered. Conclusion: This is the first large epidemiologic study on ILDs in France. Results are in the higher range of the literature, but are original for the high prevalence of secondary ILDs and the relatively low prevalence of IPF.