COPD’s early origins in low-and-middle income countries: what are the implications of a false start?

[Excerpt] The Global Initiative for chronic Obstructive Lung disease (GOLD)guideline of 2018 describes COPD as‘the result of a complexinterplay of long-term cumulative exposure to noxious gases andparticles, combined with a variety of host factors includinggenetics, airway hyper-responsiveness and poor lung growthduring childhood’.1Tobacco smoking is traditionally viewed as themain contributing factor to the development of COPD. However,COPD also occurs among non-smokers, especially in low-incomeand middle-income countries (LMICs).2,3Notably, more than 90%of COPD-related deaths occur in LMICs.4For these countries, otherrisk factors, such as ambient, occupational and household airpollution play a significant role in the development of COPD.1,2,5–7Does COPD in these settings have a different pathophysiologicaltrajectory compared to COPD in high-income countries, and if so:what does this imply?In normal lung development, airway branching is completed bythe 17th week of gestation, after which airways increase in volumeuntil young adulthood. Alveoli are present at birth and developfurther during childhood. Lung volume and airflow continue toincrease as the thorax grows, influenced by age, sex, and ethnicity,reaching a peak at young adulthood. Lung function then remainsconstant for about 10 years (the plateau phase), after which itgradually declines.8In the‘classic’COPD patient, the decline inlung function is more rapid than in healthy individuals. However,in a considerable proportion of COPD patients, lung function doesnot decline rapidly, but reaches a lower plateau phase in earlyadulthood instead. For these patients, a completely differentpathophysiological trajectory seems to lead to the diagnosis ofCOPD: the decline in lung function follows a normal pattern, yetthey seem to have a‘false start’by attaining a lower maximumlung function. [...]