Lung Function Trajectory Types in Never-Smoking Adults With Asthma: Clinical Features and Inflammatory Patterns

Area of Science:

• Pulmonary Medicine
• Respiratory Research
• Clinical Immunology

Background:

• Asthma is a heterogeneous respiratory condition with variable treatment responses.
• Identifying distinct asthma phenotypes is crucial for understanding disease progression and optimizing management.
• Longitudinal studies on lung function trajectories in adult asthmatics are limited.

Purpose of the Study:

• To investigate clinical, demographic, and inflammatory factors associated with persistent airflow limitation.
• To analyze lung function trajectories over a 1-year period in adult asthmatics.
• To identify distinct asthma phenotypes based on forced expiratory volume in 1 second (FEV1) patterns.

Main Methods:

• Serial post-bronchodilator forced expiratory volume (FEV1)% measurements were collected from 1,679 asthmatics over 1 year.
• Hierarchical cluster analysis and k-means clustering were employed to identify lung function trajectories.
• Regression methods were used to impute missing FEV1 values for comprehensive trajectory analysis.

Main Results:

• Five distinct FEV1 trajectories were identified, ranging from normal to severely decreased lung function.
• Trajectories 4 and 5 represented severe asthma, with trajectory 5 showing persistently disturbed FEV1 over 1 year.
• Trajectory 5 was associated with older age, less atopy, lower immunoglobulin E (IgE) levels, sputum neutrophilia, and higher oral steroid use compared to trajectory 4.

Conclusions:

• Trajectory clustering of FEV1 effectively identified five distinct asthma phenotypes.
• Persistent airflow obstruction in asthma may be associated with non-atopic status, low IgE, older age, neutrophilic inflammation, and low baseline FEV1.