Prevalence and incidence of interstitial lung diseases in a multi-ethnic county of Greater Paris

The objective of the study was to estimate the prevalence and incidence of interstitial lung diseases (ILDs) in Seine-Saint-Denis, a multi-ethnic county of Greater Paris, France. Patients with ILDs were identified between January and December 2012 by using several sources; all potentially involved medical specialists from public and private hospitals, community-based pulmonologists and general practitioners, and the Social Security system. Diagnoses were validated centrally by an expert multidisciplinary discussion. 1170 ILD cases were reported (crude overall prevalence: 97.9/105 and incidence: 19.4/105/year). In the 848 reviewed cases, the most prevalent diagnoses were sarcoidosis (42.6%), connective tissue diseases associated ILDs (CTDs-ILDs) (16%), idiopathic pulmonary fibrosis (IPF) (11.6%), and occupational ILDs (5.0%), which corresponded to a crude prevalence of 30.2/105 for sarcoidosis, 12.1/105 for CTDs-ILDs and 8.2/105 for IPF. The prevalence of fibrotic idiopathic interstitial pneumonias, merging IPF, nonspecific interstitial pneumonia and cases registered with code J84.1 was 16.34/105. An adjusted multinomial model demonstrated an increased risk of sarcoidosis in North Africans and Afro-Caribbeans and of CTDs-ILDs in Afro-Caribbeans, compared to that in Europeans. This study, with a comprehensive recruitment and stringent diagnostic criteria, emphasises the importance of secondary ILDs, particularly CTDs-ILDs and the relatively low prevalence of IPF, and confirms that sarcoidosis is a rare disease in France