Severe Childhood Asthma May Raise Risk of Later COPD

Children with severe asthma may be at higher risk for chronic obstructive pulmonary disease (COPD) later in life, according to a new study.

Tracking longitudinal measurements of growth and decline in lung function in patients with persistent childhood asthma may reveal links between asthma and subsequent chronic airflow obstruction, stated the researchers, led by Michael J. McGeachie, PhD, from Brigham and Women's Hospital, Harvard Medical School, Boston, MA.

"Our data support the hypothesis that both reduced growth and an early decline [in lung function] are trajectories leading to an asthma–COPD overlap syndrome and complement the recent observation that in older patients, a rapid decline in lung function can lead to COPD," they stated.

The researchers published their results in the May 12, 2016 New England Journal of Medicine.

The new study included participants from a randomized placebo-controlled study that enrolled children aged 5 to 12 years with mild to moderate asthma and followed them into their 20s. The researchers classified 684 children with asthma according to four characteristic patterns of lung-function growth and decline; patterns were based on graphs showing forced expiratory volume in 1 second (FEV₁), representing spirometric measurements performed from childhood into adulthood.

They also examined risk factors associated with abnormal patterns of growth and decline in lung-function. To define normal values, they used FEV₁ values from participants in the National Health and Nutrition Examination Survey who did not have asthma.

They found that one-quarter of the study participants had a normal pattern of lung-function growth without early decline, and three-quarters of them had abnormal patterns. Among those with abnormal patterns, 176 participants (26%) had reduced growth and an early decline, 160 participants (23%) had reduced growth only, and 178 participants (26%) had normal growth and an early decline.

Certain parameters were associated with reduced growth in lung function -- lower baseline values for FEV₁, smaller bronchodilator response, airway hyperresponsiveness at baseline, and male sex. Males were slightly more than eight times more likely to have a reduced pattern of lung growth compared with those with normal growth.

At the last spirometric measurement (~age 26 years), 73 participants (11%) met Global Initiative for Chronic Obstructive Lung Disease (GOLD) spirometric criteria for lung-function impairment that was consistent with COPD. Slightly more than one-third of the participants with a reduced lung growth pattern and 8% of those with a normal growth pattern met GOLD criteria for COPD.

The study has some limitations, the researchers acknowledged. They could not conclusively assess smoking exposure, and they did not look at genetic risk factors, prematurity, childhood respiratory infections, and other environmental exposures. Also, the follow-up may be too short to see how lung function changes affect children's health over time.

In conclusion, the researchers stated that “childhood impairment of lung function and male sex were the most significant predictors of abnormal longitudinal patterns of lung-function growth and decline. Children with persistent asthma and reduced growth of lung function are at increased risk for fixed airflow obstruction and possibly COPD in early adulthood.”

Source: McGeachie MJ, Yates KP, Zhou X for the CAMP Research Group. Patterns of growth and decline in lung function in persistent childhood asthma. N Engl J Med 2016; 374:1842-1852. DOI: 10.1056/NEJMoa1513737