Idiopathic Pulmonary Fibrosis Progression Begins Years Before Symptoms Appear
IDIOPATHIC pulmonary fibrosis (IPF) progression may begin nearly a decade before symptoms, according to new modeling research.
IPF is a chronic lung disease that causes progressive scarring of lung tissue. While the disease course after diagnosis is well documented, how it unfolds in the years leading up to diagnosis has been poorly understood. To map this earlier trajectory, investigators analyzed pulmonary function data from two patient cohorts: 245 adults with familial pulmonary fibrosis spanning subclinical to advanced stages, and 347 placebo-treated IPF patients from randomized controlled trials.
Using a Bayesian joint repeated-measures model, the team tracked four pulmonary function parameters over time and estimated disease progression relative to a defined onset point, which was the moment when diffusion capacity for carbon monoxide (DLCO) fell to 70% of predicted.
Sequential Lung Function Decline Observed
DLCO declined earliest, falling measurably about 10 years before the defined onset. By five years before onset, DLCO had already dropped to roughly 86.8% predicted; five years after onset, it had fallen further to approximately 45.3% predicted.
Forced vital capacity (FVC) followed a different pattern. Five years before onset, FVC remained near normal at about 98.6% predicted, but it dropped substantially to 76.2% predicted by five years after onset. Notably, the annual rate of FVC loss was roughly 12 times faster in the five years after onset compared to the five years before.
Outcomes worsened with disease duration. Each additional year of disease was associated with a 31% higher risk of death or lung transplantation, after adjusting for age and sex.
Implications for Clinical Trials
The results suggest that IPF follows a predictable, staged physiological decline, one that begins long before clinical presentation. Early DLCO reduction may mark the first detectable phase of disease, preceding FVC changes by several years.
These findings have direct implications for clinical trial design. Identifying patients in earlier, pre-symptomatic stages and using DLCO as a sensitive endpoint could improve the ability to detect treatment effects. The modeling framework may also help researchers investigate the biological mechanisms that initiate IPF progression.
Reference
Huang X et al. Identification of a conserved sequence of disease progression in Idiopathic Pulmonary Fibrosis. Am J Respir Crit Care Med. 2026;DOI:10.1093/ajrccm/aamag075.
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