Age-, sex-, and smoking-specific prevalence and progression in interstitial lung abnormality: patient-level meta-analysis

RATIONALE: Interstitial lung abnormalities (ILAs) are incidental computed tomography (CT) findings that often represent early, subclinical interstitial lung disease. Their prevalence and progression rates vary widely across studies, emphasizing the need to understand the impact of age, sex, and smoking for better risk stratification and management. OBJECTIVES: To evaluate the prevalence and progression rates of ILA by age, sex, and smoking intensity using individual patient-level data from global cohorts, and to analyze progression-free survival (PFS). METHODS: Systematic searches in OVID-MEDLINE and Embase identified eligible original articles reporting ILA prevalence or progression, confirmed through radiologist-reviewed CT scans. Random-effects models were used to pool estimates stratified by age, sex, and smoking intensity. Risk of bias was assessed using the Newcastle-Ottawa Scale. PFS probabilities were calculated using Kaplan-Meier analysis. RESULTS: Data from 14 studies comprising 31 739 individual subjects showed a pooled ILA prevalence of 5.6% (95% CI, 4.3%-7.3%), increasing with age from 2.5% (30 pack-years. The overall pooled progression was 34%, with fibrotic ILAs exhibiting higher progression, and age did not affect progression. PFS was evaluated in 202 individuals with ILA, with estimated rates of 76% at 3 years and 55% at 5 years. CONCLUSIONS: Age is the strongest determinant of ILA prevalence. ILAs show significant progression on imaging over time, and progression is mainly driven by fibrotic features rather than age once ILA is established. Given the higher prevalence in older adults, targeted screening in aging populations remains appropriate, while follow-up strategies should be guided by fibrotic burden rather than age.