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A cluster analysis to identify gender-specific asthma phenotypes

Published online: August 28, 2018

Asthma is a heterogeneous respiratory inflammatory disease. It is notable that gender differences may have a potential effect on asthma phenotype. The incidence and prevalence of asthma are higher in boys than in girls before puberty and higher in women than men in adulthood. Gender influences the risk of asthma in age-dependent and inflammatory patterns. T cells, specific antibodies, and pro-inflammatory mediators have been shown to be affected by sex hormones in females and males. The mechanism of the relation between gender difference and asthma still remains unclear. However, there have been no cluster analyses stratified by gender to explore potential gender-specific asthma phenotypes.

In a study recently published in The Journal of Allergy and Clinical Immunology: In Practice, Hsiao and colleagues conducted the Taiwanese Adult Asthma Cohorts (TAAC) study to enroll female (n=421) and male (n=299) adult stable asthma patients. They collected a total of 273 clinical, physiologic, and inflammatory variables. After elimination of redundant data and factor analysis, 8 variables including (1) age, (2) Body Mass Index (BMI), (3) asthma onset age, (4) pre-bronchodilator FEV1 predicted values (%), (5) pre-bronchodilator FVC predicted values (%), (6) total serum IgE, (7) blood eosinophils (%), and (8) blood neutrophils (%) were further selected for two-step cluster analyses in each gender.

Three different clusters were identified in males and females. In the female clusters, atopy/eosinophil-predominant (cluster 2), and obesity/neutrophil-predominant pattern (cluster 3) had more than a 2.5-fold risk of asthma exacerbations than non-atopy/ paucigranulocytic-predominant pattern (cluster 1). In the male clusters, current smoker/neutrophilic atopic cluster (cluster 5), and ex-smoker/eosinophil-predominant or mixed inflammatory pattern (cluster 6) also had a higher risk of asthma exacerbations than non-atopy/paucigranulocytic-predominant pattern (cluster 4).

This study identified heterogeneous characteristics between genders. In females, the analysis showed atopy with eosinophil-predominant and obese with neutrophil-predominant inflammation. Two distinct asthma phenotypes were found in current and ex-smokers in males. In practice, developing a simple, accessible clinical approach is important for the classification and management of asthma. Exploring these gender-specific sub-phenotypes may be useful for understanding the underlying mechanisms of adult asthma and may provide new directions for personalized management.

The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.

18-00082, Gender-specific asthma phenotypes, inflammatory patterns and asthma control in a cluster analysis
By Han-Pin Hsiao, Meng-Chih Lin, Chao-Chien Wu, Chin-Chou Wang, Tsu-Nai Wang