• Lung Physiology
• Child
• Clinical Epidemiology

Lung development starts already in utero whereas lung function development can be conceived to begin shortly after birth, marked by the infant’s first cry. This development progresses through adolescence until reaching its peak during early adulthood (typically between 20 and 25 years of age). However, a notable portion of the general population (4%–12%) experiences suboptimal lung development, failing to attain normal peak lung function in early adulthood.1 This phenomenon is linked to an increased prevalence and earlier onset of respiratory, cardiovascular and metabolic disorders, as well as premature mortality. Recent evidence suggests that within the general population, diverse lung function trajectories exist from birth to early adulthood, including high, normal and low trajectories. However, certain subgroups deviate from these trajectories, exhibiting catch-up (where lung function starts from a lower trajectory but progresses to higher ones) or growth failure (where lung function starts from a normal or higher trajectory but declines to lower ones) in lung function development (figure 1).2 Therefore, intervening during this critical period to promote healthy lung function development may result in enhanced respiratory health and overall well-being throughout the lifespan.