Figure 2.

Text mining using VOSviewer (titles and abstracts). Note: the colors of each node were automatically assigned by VOSviewer based on its score; the node size was based on the frequency of each term; the length and thickness of the lines reflected the association between two terms. Cluster 1 (red) refers to comorbidity and COPD; cluster 2 (blue) focuses on interventions and treatment to increase QoL of people with COPD, cluster 3 (yellow) points out the risk and mortality of exacerbation of COPD.