Environmental and occupational exposures and the risk of idiopathic pulmonary fibrosis: A systematic review

Purpose. Idiopathic pulmonary fibrosis (IPF) is defined as a specific form of chronic, progressive, fibrosing interstitial pneumonia. The recognition of the risk factors for IPF is mandatory for disease prevention. The aim of the present systematic review is to evaluate the association between occupational and environmental exposures and the risk of IPF. Methods. Original observational studies published before July 3rd (2020) were identified through electronic searches of the PubMed, Embase, Cochrane and Web of Science databases. To meet the inclusion criteria, studies had to describe the exposure assessment, and the diagnosis had to be based on clinical history, computed tomography (CT) and/or histology. Results. Eight studies met the inclusion criteria for the systematic review, including a total of 2084 patients. A quantitative meta-analysis could not be performed due to the heterogeneity of the studies. Smoking was associated with an increased risk of IPF, but there was no clear dose-response relationship for smoking years and pack-years consumption. Exposure to birds and occupational exposure to metal and organic dust at work were also associated with the risk of IPF. Conclusions. This systematic review revealed an association between smoking, exposures to birds and cat allergens and occupational exposures to metal, wood and organic dusts and the risk of IPF, although the findings were controversial among the studies. Further investigations should integrate genetic susceptibility analysis, dose-response relationships, and direct measures of exposure, performing adjustments for possible confounders.