Patterns of Growth and Decline in Lung Function in Persistent Childhood Asthma

Abstract

Background: 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.

Methods: We classified children with asthma according to four characteristic patterns of lung-function growth and decline on the basis of graphs showing forced expiratory volume in 1 second (FEV1), representing spirometric measurements performed from childhood into adulthood. Risk factors associated with abnormal patterns were also examined. To define normal values, we used FEV1 values from participants in the National Health and Nutrition Examination Survey who did not have asthma.

Results: Of the 684 study participants, 170 (25%) had a normal pattern of lung-function growth without early decline, and 514 (75%) had abnormal patterns: 176 (26%) had reduced growth and an early decline, 160 (23%) had reduced growth only, and 178 (26%) had normal growth and an early decline. Lower baseline values for FEV1, smaller bronchodilator response, airway hyperresponsiveness at baseline, and male sex were associated with reduced growth (P<0.001 for all comparisons). At the last spirometric measurement (mean [±SD] age, 26.0±1.8 years), 73 participants (11%) met Global Initiative for Chronic Obstructive Lung Disease spirometric criteria for lung-function impairment that was consistent with chronic obstructive pulmonary disease (COPD); these participants were more likely to have a reduced pattern of growth than a normal pattern (18% vs. 3%, P<0.001).

Conclusions: 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. (Funded by the Parker B. Francis Foundation and others; ClinicalTrials.gov number, NCT00000575.).

Figure 1. Longitudinal Lung-Function Trajectories

Possible lung-function trajectories during the first three decades of life are shown; the lung function plotted for each age is the percentage of the maximum forced expiratory volume in 1 second (FEV₁) in a person without lung disease; the maximum value is usually attained at the age of 18 to 30 years. A normal pattern of lung-function growth and decline is characterized by a steep increase during adolescence, a plateau in early adulthood, and a gradual decline into old age. Abnormal trajectories include reduced growth, normal growth and an early decline, and reduced growth and an early decline. The red brackets indicate FEV₁ criteria according to Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage 2 (FEV₁ ≥50% and <80%) and stage 3 (FEV₁ ≥30% and <50%) of chronic obstructive pulmonary disease (COPD), when accompanied by a ratio of FEV₁ to forced vital capacity that is less than 0.70. The figure is adapted from Speizer and Tager.

Figure 2. Average Prebronchodilator FEV₁ Trajectories for 684 Study Participants According to Pattern Classification, as Compared with FEV₁ in Persons without Asthma

Values for prebronchodilator FEV₁ in the study participants are group averages and are based on robust, locally weighted scatterplot smoothing regression. Also shown are percentiles of FEV₁ in persons without asthma who were participants in the third National Health and Nutrition Examination Survey (NHANES III) and were matched to our study participants for sex, race or ethnic group, age, and height at each spirometric session. Panel A shows the average FEV₁ trajectory for participants classified as having normal lung-function growth without an early decline (170 participants), Panel B shows the trajectory for participants who had reduced growth without an early decline (160 participants), Panel C shows the trajectory for participants with normal growth and an early decline (178 participants), and Panel D shows the trajectory for participants who had reduced growth and an early decline (176 participants).