Interstitial Lung Disease Epidemiology in the Past Three Decades: A Narrative Review.

Current epidemiological data on interstitial lung disease (ILD) are still poor. The principal cause of the discordant data is associated with a heterogeneous group of respiratory diseases that includes a large number, about 200 families, with low frequency, distinct and sometimes unknown etiology, and different progression. In fact, some conditions spontaneously resolve, whereas others, such as IPF and most non-IPF ILDs, progress to respiratory failure and death despite treatment. Furthermore, epidemiological data are limited. The scope of the narrative review is to report ILD incidence and prevalence in registries from different countries in the last three decades. We identified 20 ILD registries (17 prospective and 3 retrospective) from major countries in Europe (n = 10), Asia (n = 7), North America (n = 2), and Oceania (n = 1). Significant discrepancies in ILD and ILD subtype prevalence and incidence among countries are reported in registries. These discrepancies could be determined by different ethnicities and socioeconomic conditions as well as by updates in disease diagnosis and classification. ILD epidemiological registries are progressively ameliorating through better adherence to updated guidelines and classification codes. An accurate and definite diagnosis and compilation of ILD epidemiological registries will be useful for a more precise monitoring of disease progression and treatment. Future research to identify the populations with the highest risk factors, including genetic and molecular studies, and implementation of disease progression scores are needed to improve ILD clinical assessment.