Impact of medications on lung function in fibrotic hypersensitivity pneumonitis

Hypersensitivity pneumonitis (HP) is primarily managed through antigen avoidance. However, symptoms often persist even after avoidance, necessitating systemic therapies such as glucocorticoids, immunosuppressants, and antifibrotic agents. The impact of these medications on pulmonary function remains uncertain. To clarify the effects of these systemic therapies on lung function in fibrotic HP, we conducted a retrospective cohort study analyzing longitudinal pulmonary function data.

Patients were identified at our center. Changes in lung function before and after treatment initiation were analyzed using linear mixed effects model and interrupted time series analysis. Multivariate analysis adjusted for age, sex, and smoking history.

A total of 388 patients were included. Multivariate regression analysis revealed an annual decline in forced vital capacity (FVC) percent predicted of 3.16 % (95 % confidence interval: 2.73-3.58). Untreated patients had a slower decline (1.68 % per year, 95 % confidence interval: 0.83-2.52), while treated patients showed a reduction in annual decline from 6.96 % (95 % confidence interval: 6.27-7.65) before treatment to 3.03 % thereafter (P < 0.001). Glucocorticoids alone reduced the decline from 6.96 % (95 % confidence interval: 5.57-8.34) to 0.32 % per year (P < 0.001), while antifibrotic agents slowed it from 4.24 % (95 % confidence interval: 3.09-5.40) to 1.24 % per year (P < 0.001).

Systemic therapies, particularly glucocorticoids and antifibrotic agents, significantly slow the decline in FVC percent predicted in patients with fibrotic HP. Prospective trials are needed to confirm these findings.