Transitions Among Four Spirometric States and Subsequent Pre-Bronchodilator Airflow Obstruction: A Community Cohort...

To compare short-term transitions among four pre-bronchodilator spirometric states, assess subsequent airflow obstruction risk by baseline state and the distribution of these states among observed events, and examine the association between repeated isolated spirometry-defined small-airway dysfunction (sSAD) and subsequent airflow obstruction.

We analyzed spirometry data from three Chinese community cohorts (2019-2023). Modified Poisson regression assessed subsequent pre-bronchodilator airflow obstruction (AFO) by baseline state. Logistic models additionally adjusted for baseline FEV₁/FVC. Repeated isolated sSAD was examined using bias-reduced logistic models before and after adjustment for prior FEV₁/FVC values.

Among 13,220 participants, 74.1% retained their baseline state. Among 11,551 without baseline AFO, follow-up AFO proportions were 0.61%, 8.11% and 18.60% for preserved spirometry, isolated sSAD and preserved ratio impaired spirometry (PRISm), respectively. In logistic models, additional baseline FEV₁/FVC adjustment reduced standardized risk ratios from 12.44 to 2.33 (95% CI 1.58-3.44) for isolated sSAD and from 26.75 to 4.32 (2.69-6.92) for PRISm. Baseline isolated sSAD accounted for 392 of 492 AFO events (79.7%). Among 3947 participants with preserved spirometry or isolated sSAD at both initial examinations, the OR for two versus no isolated-sSAD detections decreased from 34.49 (12.02-99.00) to 1.99 (0.63-6.31; P=0.242) after adjustment for both prior FEV₁/FVC values.

PRISm was associated with the highest subsequent pre-bronchodilator AFO risk, whereas most events occurred in participants with baseline isolated sSAD. Associations were attenuated but persisted after baseline FEV₁/FVC adjustment. The repeated-sSAD association was attenuated and no longer statistically significant after adjustment for both prior ratios.