Risk Factors Associated With Mortality in Hypersensitivity Pneumonitis: A Meta-analysis

Purpose: Hypersensitivity pneumonitis (HP), an immune-mediated form of diffuse parenchymal lung disease (DPLD), is triggered by inhalation of a wide variety of allergens in susceptible individuals. Several studies suggest that the death rate associated with this disease has increased significantly in recent years. This meta-analysis investigates the significant clinico-radiological characteristics which may be appraised as potential risk factors associated with disease mortality.Methods: Extensive literature search was conducted for original articles published between January 2009 and April 2021 through PubMed, Google Scholar, EMBASE, and Cochrane Library using the keywords: “hypersensitivity pneumonitis”, “hazard ratio” and “mortality”. Results: A total of 21 independent studies related to mortality of HP subjects could be identified. The combined results of univariate and multivariate analysis suggest that older age [univariate odds ratio (OR) 1.038 (1.028-1.048); multivariate OR 1.036, (1.025-1.046)], male subjects [univariate OR 1.508, (1.240- 1.834); multivariate OR 1.396, (1.004-1.943)], honeycombing [univariate OR 1.086 (1.065- 1.108); multivariate OR 1.121 (1.070- 1.175)] and traction bronchiectasis [univariate OR 1.141 (1.092- 1.192); multivariate OR 1.107 (1.048-1.169)] are significantly associated with mortality risk of HP subjects. Further, forced vital capacity (FVC), diffusing capacity for carbon monoxide (DLco), ground glass opacity (GGO) and mosaic attenuation were associated with lower risk of all-cause mortality. Although smoking status correlated with mortality risk in these patients, the findings appeared to be insignificant. Conclusion: Individual male subjects with older age and presence of extensive fibrosis, i.e., honeycombing and traction bronchiectasis experience an increased mortality risk.