Interstitial lung diseases (ILDs) are a heterogeneous group of pathologies and some of them may have progressive nature with accelerated lung function (LF) decline.

The aim of the study was to assess survival and possible risk factors for mortality in a big cohort of ILDs patients observed over 11 years with accessible at least two observations no less than a year apart.

Methods: retrospective analysis of ILDs patients in the tertiary reference center for lung diseases covered the period 01?2009 to 03?2020. Clinical data (diagnosis) and lung function tests (spirometry and lung transfer factor - TLco) results at the first and last presentations were included in the statistic model.

Results: the group consisted of 2497 ILDs patients mainly with sarcoidosis (46.8%), fibrotic ILD (J84.1; 13.9%), other ILDs (J84.8, J84.9; 30%), and hypersensitivity pneumonitis (9.3%). At the first presentation LF tests revealed airway obstruction in 15.7%, restrictive pattern in 28%, and low TLco in 52.3% of these patients. Accelerated yearly decline (>5% of FVC or >10% of TLco) was found in 6.9% and 2.4% of patients respectively.  The median observation time was 6.7 (IQR 3.3 to 9.9) years. 274 patients (11%) died in the observed period.

Survival analysis revealed that accelerated LF decline was associated with prognosis. The multivariable model (Cox hazard) indicated that decline of FVC (HR 4.1) and TLco (HR 3.5), age, baseline FVC and TLco, and diagnosis of fibrotic ILD (HR 4.1) or other ILD (HR 2.4), but not airway obstruction nor hypersensitivity pneumonitis were independent factors associated with overall mortality.

Conclusion: Accelerated declines in FVC or TLco are independent factors affecting prognosis in ILDs patients.