# Small Airway Function as an Indicator for Persistent Airflow Limitation Asthma: A Retrospective Study

## TL;DR

This study shows that persistent airflow limitation asthma is more common in elderly male smokers and has worse small airway function, which may need targeted treatment.

## Contribution

The study identifies small airway dysfunction as a key indicator and potential treatment target for PAL asthma.

## Key findings

- PAL asthma is more common in elderly male smokers with higher severity and poorer control.
- Small airway function in PAL asthma improves less after bronchodilators compared to non-PAL asthma.
- Smoking index and ACT score are independent risk factors for PAL asthma.

## Abstract

Asthma is a heterogeneous disease characterized by chronic inflammatory changes in the airways and reversible airflow limitation. Persistent airflow limitation (PAL) asthma, as a common phenotype of asthma, is usually defined as forced expiratory volume in 1 s/forced vital capacity (FEV1/FVC) ratio lower than 0.7 after bronchodilator in asthmatic patients. Recent research has indicated a correlation between PAL asthma and more frequent asthma exacerbations.

A total of 1322 asthma patients were retrospectively assessed, and finally, 441 asthma patients were included in the study. Among them, 217 patients were diagnosed with non‐PAL asthma, and 224 patients were PAL asthma. The differences in basic information, clinical manifestations, lung function, and laboratory test indicators between the PAL asthma and non‐PAL asthma groups were compared. A clinical prediction model for PAL asthma based on patient demographics was established using logistic regression analysis.

Comparing the demographic data of patients with PAL and non‐PAL asthma, it was observed that PAL asthma was more common in elderly smoking males. Patients with PAL asthma had a higher severity of asthma, poorer control, and lower life quality compared to non‐PAL asthma. In terms of lung function, patients with PAL asthma mainly exhibited obstructive ventilatory impairment, small airway dysfunction, diffusion dysfunction, and increased residual volume. Notably, after bronchodilators, patients with PAL asthma showed a significantly lower rate of improvement in small airway function compared with non‐PAL asthma. Logistic regression analysis showed gender, smoking index, and Asthma Control Test (ACT) score were independent risk factors for PAL asthma. Linear regression analysis showed small airway function was closely associated with ACT score.

PAL asthma was poorly controlled, leading to a diminished quality of life. The limited improvement in small airway function after bronchodilator in PAL asthma suggested that targeting small airway dysfunction may hold significant value in the treatment of PAL asthma.

This retrospective study (441 asthma patients) found that PAL asthma is more common in elderly males, with smoking index and ACT score as its independent risk factors. PAL patients have poor small airway function and limited improvement after bronchodilators, suggesting targeting small airways may effective for PAL asthma treatment.