Abstract
The global incidence and prevalence of interstitial lung disease (ILD) are difficult to determine due to the rarity of the condition, inconsistent case ascertainment and reporting methods, and differences in risk factors, burden of exposures, and access to health-care systems across geographical areas. With these caveats, several studies have reported an increased incidence and prevalence of ILD over time. Idiopathic pulmonary fibrosis is the most common and extensively studied ILD, whereas connective tissue disease-associated ILD and hypersensitivity pneumonitis display the most geographical variability. Except for idiopathic pulmonary fibrosis, connective tissue disease-associated ILD, hypersensitivity pneumonitis, and sarcoidosis, few data are available for other ILDs. Access to health care remains uneven particularly in low-income and middle-income countries, leading to major health disparities. Socioeconomic inequalities also affect morbidity and mortality within and across countries. We performed a non-systematic review of the most recent literature on the epidemiology and burden of ILD, and highlighted areas where substantial gaps in knowledge remain and further studies are needed. The introduction of new tools, including nationwide health-care databases and monitoring of air pollution exposure, is opening new avenues for ILD epidemiology research; however, we are only at the beginning of understanding how the interaction between genetic and environmental factors contributes to the rising burden of these deadly diseases.