The association between childhood asthma and adult chronic obstructive pulmonary disease.
Thorax. 2014 Sep;69(9):805-10.
- 1Department of Respiratory and Sleep Medicine, Women’s and Children’s Hospital, Adelaide, South Australia, Australia.
- 2Murdoch Children’s Research Institute, Melbourne, Victoria, Australia.
- 3Royal Children’s Hospital Melbourne, Melbourne, Victoria, Australia.
- 4Department of Allergy, Immunology and Respiratory Medicine, The Alfred Hospital, Prahran, Victoria, Australia.
- 5Murdoch Children’s Research Institute, Melbourne, Victoria, Australia Respiratory Medicine, Royal Children’s Hospital Melbourne, Parkville, Victoria, Australia.
INTRODUCTION: There is epidemiological evidence to suggest that events in childhood influence lung growth and constitute a significant risk for adult COPD. The aim of the study is to evaluate for an association between childhood asthma and adult COPD.
METHODS: This longitudinal, prospective study of 6-7-year-old children with asthma has been regularly reviewed every 7 years to the current analysis at 50 years of age. Participants completed respiratory questionnaires and lung function spirometry with postbronchodilator response. At the age of 50, subjects were classified to the following subgroups: non-asthmatics, asthma remission, current asthma and COPD which was defined by FEV1 to FVC ratio postbronchodilator of less than 0.7.
RESULTS: Of the remaining survivors, 346 participated in the current study (participation rate of 76%) of whom 197 completed both questionnaire and lung function testing. As compared with children without symptoms of wheeze to the age of 7, (non-asthmatics) children with severe asthma had an adjusted 32 times higher risk for developing COPD (95% CI 3.4 to 269). In this cohort, 43% of the COPD group had never smoked. There was no evidence of a difference in the rate of decline in FEV1 (mL/year, 95th CI) between the COPD group (17, 10 to 23) and the other groups: non-asthmatics (16, 12 to 21), asthma remission (20, 16 to 24) and current asthma (19, 13 to 25).
CONCLUSIONS: Children with severe asthma are at increased risk of developing COPD.
KEYWORDS: asthma; chronic obstructive pulmonary disease
Chronic obstructive pulmonary disease (COPD) is a very common condition affecting the worldwide population. The Global Burden of Disease Study has projected that COPD, which ranked sixth as the cause of death in 1990, will become the fourth leading cause of death worldwide by 2030. Over the last few years, there has been recent interest in understanding the origins of chronic obstructive pulmonary disease.
There is epidemiological evidence to suggest that events in childhood influence lung growth and constitute a significant risk for the development of COPD. There are few prospective community studies which have explored the long term outcome of childhood asthma into adult life.
The Melbourne asthma cohort is a unique study where 7 year old children were recruited randomly from a community sample in 1964 and followed up at regular intervals to the age of 50 years, therefore allowing the assessment of chlidhood risks towards adult COPD. In this cohort, different groups of children were recruited including children with intermiitent asthma, severe asthma and those with no asthma. At age 50 years, adults with COPD were defined by standardized and validated lung function measurements. The study found that children with severe asthma had a 37 fold increase risk of having COPD at the age of 50 years but the risk was not noted in those with intermittent asthma. Of note, in the group with COPD, 43% had reported no previous history of smoking. Lung function when measured was also reduced in the group who had COPD at the age of 50 years and that this deficit was evident from the first lung function testing at the age of 7 years. The results of this study highlights the importance of suboptimal lung function growth in childhood as a predisposing factor towards adult COPD and that airway remodelling may be occuring early in life. It is also of interest that a substantial group of adults with COPD did not report a smoking history adding to the heterogenous nature of COPD.
One of the limitations of the study is that the children with severe asthma may not be representative of current children with severe asthma as subjects in this cohort were also managed at a time when corticosteroids were not available in clinical practice until they were in their late 20’s or 30’s. Recent studies of asthmatic cohorts demonstrate that inhaled corticosteroids do not influence the natural outcome of asthma but these studies were limited to those with mild asthma only.
This review highlights the importance of surveillance of children with asthma and their lung function measurements particularly those with a more severe phenotype. It is unclear as to whether early intervention of therapy such as inhaled corticosteroids will have long term implications on the outcome in adult life but we await with interest on some of the current birth cohorts as they are followed into adult life.
Future directions in research should focus on studies in the preschool years which appear to be the period when changes of airway remodeling are occurring. Importantly, research needs to continue into understanding the mechanisms that precede airway remodeling. Ideally, airway epithelial biopsies would provide the most information but given its invasive nature further non invasive tools need to be evaluated. High resolution CT chest in adults has shown good correlation between lung function indices of airflow obstruction and features of airway remodeling but this has not been established in children. Noninvasive techniques to measure airway inflammation and biomarkers should be explored in preschool children. Lastly further research into candidate would also be of interest.
In summary, children with asthma, particularly those with a more severe phenotype are at increased risk of developing COPD and it is crucial to follow these children into adult life and to treat effectively with the hope of minimizing the outcome of COPD.