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

• Published in: Allergy, asthma & immunology research Vol. 10; no. 6; pp. 614 - 627
• Main Authors: Kim, Joo-Hee, Chang, Hun Soo, Shin, Seung Woo, Baek, Dong Gyu, Son, Ji-Hye, Park, Choon-Sik, Park, Jong-Sook
• Format: Journal Article
• Language: English
• Published: Korea (South) Korean Academy of Asthma, Allergy and Clinical Immunology 01.11.2018; The Korean Academy of Asthma, Allergy and Clinical Immunology; The Korean Academy of Pediatric Allergy and Respiratory Disease; 대한천식알레르기학회
• Subjects: Adults; Air flow; Airway management; Asthma; Atopy; Cluster analysis; Clustering; Correlation analysis; Demographics; Immunoglobulin E; Inflammation; Leukocytes (eosinophilic); Leukocytes (neutrophilic); Longitudinal studies; Lungs; Neutrophilia; Original; Phenotypes; Regression analysis; Respiratory function; Respiratory tract; Smoking; Sputum; Steroid hormones; Steroids; Trajectory analysis; Vector quantization; 내과학; phenotype; forced expiratory volume; Adult; asthma; disease progression; inflammation
• ISSN: 2092-7355; 2092-7363; 2092-7363
• DOI: 10.4168/aair.2018.10.6.614

Asthma is a heterogeneous disease that responds to medications to varying degrees. Cluster analyses have identified several phenotypes and variables related to fixed airway obstruction; however, few longitudinal studies of lung function have been performed on adult asthmatics. We investigated clinical, demographic, and inflammatory factors related to persistent airflow limitation based on lung function trajectories over 1 year. Serial post-bronchodilator forced expiratory volume (FEV) 1% values were obtained from 1,679 asthmatics who were followed up every 3 months for 1 year. First, a hierarchical cluster analysis was performed using Ward's method to generate a dendrogram for the optimum number of clusters using the complete post-FEV1 sets from 448 subjects. Then, a trajectory cluster analysis of serial post-FEV1 sets was performed using the k-means clustering for the longitudinal data trajectory method. Next, trajectory clustering for the serial post-FEV1 sets of a total of 1,679 asthmatics was performed after imputation of missing post-FEV1 values using regression methods. Trajectories 1 and 2 were associated with normal lung function during the study period, and trajectory 3 was associated with a reversal to normal of the moderately decreased baseline FEV1 within 3 months. Trajectories 4 and 5 were associated with severe asthma with a marked reduction in baseline FEV1. However, the FEV1 associated with trajectory 4 was increased at 3 months, whereas the FEV1 associated with trajectory 5 was persistently disturbed over 1 year. Compared with trajectory 4, trajectory 5 was associated with older asthmatics with less atopy, a lower immunoglobulin E (IgE) level, sputum neutrophilia and higher dosages of oral steroids. In contrast, trajectory 4 was associated with higher sputum and blood eosinophil counts and more frequent exacerbations. Trajectory clustering analysis of FEV1 identified 5 distinct types, representing well-preserved to severely decreased FEV1. Persistent airflow obstruction may be related to non-atopy, a low IgE level, and older age accompanied by neutrophilic inflammation and low baseline FEV1 levels.