Research in context
Evidence before this study
Although accelerated lung function decline has been shown to be associated with development of chronic obstructive pulmonary disease (COPD), the relationship between the full expression of lung function—encompassing an individual's lifetime trajectory capturing both growth and decline—and COPD has never been reported. We searched for articles in PubMed from inception up to July 28, 2017 using the search terms “lung function”, “growth”, “decline”, “pattern*”, and “trajector*”. From 266 identified papers, only two classified lung function trajectories on the basis of more than two repeated lung function measurements. However, one was restricted to participants with childhood asthma and both were unable to capture the lung function decline phase due to duration of the follow-up (maximum age at last measurement being 32 years). Additionally, understanding how child and adult factors interact to determine membership of healthy as well as adverse lifetime trajectories is crucial to inform lifetime preventive strategies and promote lung health. Such evidence does not currently exist.
Added value of this study
Our findings of associations between distinct lung function trajectories and risk of COPD provide novel insights into the role of lifetime lung function trajectories in the course of COPD, and show the potential for interventions that promote healthy lung function and reduce COPD risk. Our study is the first to model lung function trajectories from childhood to the sixth decade of life in a general population. We identified six distinct trajectories. Three trajectories exhibiting lower lung function in childhood with subsequent normal or accelerated decline had increased risk of COPD and collectively accounted for most COPD cases. Most importantly, moderate–severe COPD cases arose only from these three trajectories. Early life factors including allergic diseases, lung infections, parental asthma, and maternal smoking predicted three unfavourable lung function trajectories. Personal smoking amplified the effect of maternal smoking on belonging to the worst lung function trajectory.
Implications of all the available evidence
Reduction of maternal smoke exposure and personal smoking and encouragement of immunisation are identified as public health targets to prevent adverse lung function trajectories and reduce future COPD burden. Clinicians and patients with asthma should be made aware of the potential long-term implications of non-optimal asthma control throughout life, and this should be investigated in future intervention trials.