Radiologic emphysema is increasingly observed in patients with asthma, yet its prognostic significance remains unclear. This study aimed to evaluate whether emphysema identified on chest computed tomography (CT) predicts accelerated lung function decline among asthma patients.

We conducted a retrospective cohort study of adult asthma patients who received inhaled corticosteroid therapy and underwent serial pulmonary function tests over a minimum follow-up of one year at two tertiary hospitals. Radiologic emphysema was identified via visual CT assessment, and patients were stratified into emphysema and non-emphysema groups. Annual changes in forced expiratory volume in 1 s (FEV ₁ ) and FEV ₁ /forced vital capacity ratio (FVC) were analysed using multivariable linear mixed-effects models. Sensitivity analyses assessed rapid lung function decline using multivariable logistic regression.

Of 351 patients included, 117 (33.3 %) had radiologic emphysema. The emphysema group showed significantly greater annual declines in FEV ₁ (−38.7 vs. −7.8 mL/year) and FEV ₁ /FVC (−0.62 %/year vs. 0 %/year). Emphysema was independently associated with accelerated decline in both parameters after full adjustment (FEV ₁ : β = −12.5 mL/year, 95 % CI: −18.9 to −6.2; FEV ₁ /FVC: β = −0.31 %/year, 95 % CI: −0.47 to −0.15; both P  <  0.001). Sensitivity analyses confirmed increased odds of rapid decline (adjusted OR for FEV ₁ : 2.232; FEV ₁ /FVC: 2.231).

Radiologic emphysema defines a distinct asthma phenotype associated with progressive airflow limitation. Integrating structural imaging into routine asthma assessment may enhance risk stratification and guide individualized management.