Data indicate that COPD is now a leading cause of premature death and chronic health burden worldwide Additionally, asthma-COPD overlap syndrome (ACOS) is an emerging issue posing challenges regarding treatment. Given the increasing burden of these conditions, understanding their origins may help improve future treatment and prevention options.
A New Focus
Emerging evidence points to the importance of early life origins of COPD and ACOS, leading to hypotheses such as childhood lung function impairment possibly tracking through to adulthood. And while lower peak lung function attained by early adulthood is effectively a lower baseline from which accelerated decline from exposure to respiratory hazards (eg, smoking) can occur, the majority of research focused on COPD and ACOS have assessed adult life-related risk factors and interventions. For a study published in the American Journal of Respiratory and Critical Care Medicine, Dinh Bui, PhD-candidate Shyamali Dharmage, PhD, and colleagues sought to determine whether children with reduced lung function would be at an increased risk of developing mid-life COPD and ACOS.
“The study is based on data from the Tasmanian Longitudinal Health Study (TAHS), one of the world’s longest ongoing cohort studies,” explains Dr. Dharmage. TAHS was initiated in 1968 in Tasmania, Australia. More than 8,500 children born in 1961 underwent pre-bronchodilator (BD) spirometry at age 7. This study was then followed up frequently. During the 2002-2006 follow-up, when participants were aged 45, a sub-sample underwent pre- and post-BD spirometry. Among this sub-sample, researchers analyzed the link between lung function in childhood and the risk of middle-age COPD and ACOS using multinomial regression.
Uncovering a Link
Among study participants, population prevalence rates at age 45 were 13.5% for asthma alone, 4.1% for COPD alone, and 2.9% for ACOS. Overall, children with lung function in the lowest quartile were at the highest risk of developing COPD and ACOS even when their lung function was within the normal range, says Dr. Dharmage. In fact, the lowest quartile of FEV1 at 7 years was associated with ACOS (odds ratio [OR], 2.93), but not COPD or asthma alone. “Compared with the highest quartile of FEV1/FVC ratio at age 7, there are 5.7- and 16.3-fold increases in the risk of having COPD and ACOS in middle age, respectively, for those in the lowest quartile,” adds Bui.
However, the lowest quartile of FEV1/FVC ratio at age 7 was not associated with increased risk of asthma alone. “In our analysis, COPD and ACOS were defined by lung function while, by definition, asthma alone did not have fixed air flow obstruction,” explains Bui. “Moreover, having lung function deficits over a long period is likely to lead to more fixed than reversible air flow obstruction.”
The study findings provide evidence of another long-term pathway to COPD from poor lung function in childhood, according to the study authors. “Moreover, the data show that those with COPD, and particularly ACOS, in middle age displayed persistently lower lung function through life than did healthy peers,” Dr. Dharmage says (Figure). “This is consistent with prior research tracking lung function across the life course.”
Dr. Dharmage hopes the study will increase awareness about the opportunity to lessen COPD and ACOS burden and encourage physicians to consider measuring lung function at a younger age for children considered to be at risk. “Our findings suggest that we can at least reduce part of COPD and ACOS burden by targeting the pathway from reduced lung function in early life,” she adds. “We suggest physicians to routinely follow children first seen with reduced lung function, such as those with lung function below the lower limit of normal, in order to identify the high risk group and prioritize care and treatment.”
Bui D, Burgess J, Lowe A, et al.. Childhood Lung Function Predicts Adult Chronic Obstructive Pulmonary Disease and Asthma–Chronic Obstructive Pulmonary Disease Overlap Syndrome. Am J Respir Crit Care Med. 2017;196(1):39-46. Available at www.atsjournals.org/doi/abs/10.1164/rccm.201606-1272OC.