Examining the association between asthma and CAO: A global cross-sectional study

Abstract

ABSTRACT

BACKGROUND: Chronic airflow obstruction has been associated with asthma in high-income countries. Whether this is true in low-income countries, where chronic airflow obstruction and tobacco smoking are less common, it is unknown. OBJECTIVE: This project aimed to assess the association of chronic airflow obstruction with doctor-diagnosed asthma and whether this association is consistent across different regions of the world. MATERIAL AND METHODS: Data from 28,815 adults, from 41 sites of the Burden of Obstructive Lung Disease (BOLD) study, who had provided acceptable post-bronchodilator spirometry measurements, and information on doctor-diagnosed asthma were included. The association of airflow obstruction with asthma was assessed within each site, using regression analysis, followed by meta-analysis. Estimates were stratified by geographic region. In a sensitivity analysis, the same regression model was run after participants with current asthma were excluded. All models were adjusted for potential confounders. MAIN RESULTS: Participants who had been diagnosed with asthma were more likely to have chronic airflow obstruction than those who had never been diagnosed with asthma (odds ratio = 4.96, 95% confidence interval 4.39 – 5.61). This positive association was consistent across sites, but was markedly heterogeneous (I2 = 70.2%, p < 0.001). The high heterogeneity was partially explained by geographical differences. In the sensitivity analysis, excluding participants with current asthma, the association between chronic airflow obstruction and asthma remained significant but was weaker (odds ratio = 2.41, 95% confidence interval 1.96 – 2.97). CONCLUSION: An asthma diagnosis is a good predictor of chronic airflow obstruction. However, the strength of this association varies across the world and the comprehensive reasons for this variation are not clear yet.