Research Square · Oct 23, 2026
Longitudinal Pulmonary Function Progression and Risk of New-Onset Airflow Obstruction in SAD and PRISm: a Multi-Center Population-Based Cohort Study in Southwest China
By Li Y, Chen C, Lei Y et al.
Background Small-airway dysfunction (SAD) and preserved-ratio impaired spirometry (PRISm) may precede persistent airflow obstruction, yet longitudinal data on pulmonary function progression and incident airflow obstruction in these phenotypes remain limited. Methods We analysed 10,692 adults from community spirometry-screening programmes in Southwest China, each with at least two quality-controlled examinations. Spirometry-defined airflow obstruction was defined as FEV1/FVC < 0.70; PRISm as FEV1/FVC ≥ 0.70 with FEV1 < 80% predicted; and SAD as FEV1/FVC ≥ 0.70 with at least two of MMEF, FEF50, and FEF75 < 65% predicted. Baseline spirometric phenotypes were categorized into five groups: normal spirometry, isolated SAD, isolated PRISm, PRISm with SAD, or airflow obstruction. Incidence rates were quantified per 1,000 person-years. Cox proportional hazards regression was used to identify risk factors associated with incident airflow obstruction, while random-intercept linear mixed-effects models were applied to characterize longitudinal FEV1 trajectories. Results At baseline, 5,054 participants (47.3%) had normal spirometry, 4,034 (37.7%) had isolated SAD, 24 (0.2%) had isolated PRISm, 277 (2.6%) had PRISm with SAD, and 1,303 (12.2%) had airflow obstruction. Among 9,389 participants without baseline airflow obstruction, 490 developed incident airflow obstruction during 21,804 person-years of follow-up (incidence rate: 22.5 per 1,000 person-years; cumulative risk: 5.22%). Phenotype-specific cumulative risks were 0.65% for normal spirometry, 9.77% for isolated SAD, 8.33% for isolated PRISm, and 22.02% for PRISm with SAD. Compared with normal spirometry, isolated SAD, isolated PRISm, and PRISm with SAD were all independent risk factors for incident airflow obstruction, with adjusted hazard ratios (HRs) of 12.01, 7.69, and 20.53, respectively, in the complete-case Cox model. Additional significant risk factors included male sex (adjusted HR 1.85) and current smoking (adjusted HR 1.44). The model yielded an apparent C-index of 0.843. The displayed phenotype-specific trajectories showed estimated annual FEV1 changes of -47.0 mL/year for normal spirometry, -37.0 mL/year for isolated SAD, + 3.2 mL/year for PRISm with SAD, and − 30.9 mL/year for airflow obstruction under the reference covariate profile. Conclusions Spirometry-defined SAD and PRISm identified heterogeneous short-term risks of incident airflow obstruction, with the highest risk in PRISm with SAD. These screening phenotypes require confirmation and should not be interpreted as clinical diagnoses in isolation. Trial registration: Chinese Clinical Trial Registry, ChiCTR1900024623. Registered 19 July 2019, before the first participant was enrolled.