Relationships between lung function, allergy, and wheezing in urban children

Abstract

Background: Allergic sensitization and low lung function in early childhood are risk factors for subsequent wheezing and asthma. However, it is unclear how allergic sensitization affects lung function over time.

Objective: We sought to test whether allergy influences lung function and whether these factors synergistically increase the risk of continued wheezing in childhood.

Methods: We analyzed longitudinal measurements of lung function (spirometry and impulse oscillometry) and allergic sensitization (aeroallergen skin tests and serum allergen-specific IgE) throughout early childhood in the Urban Environmental and Childhood Asthma study, which included high-risk urban children living in disadvantaged neighborhoods. Intraclass correlation coefficients were calculated to assess lung function stability. Cluster analysis identified low, medium, and high allergy trajectories, which were compared with lung function and wheezing episodes in linear regression models. A variable selection model assessed predictors at age 5 years for continued wheezing through age 12 years.

Results: Lung function adjusted for growth was stable (intraclass correlation coefficient, 0.5-0.7) from age 5 to 12 years and unrelated to allergy trajectory. Lung function and allergic sensitization were associated with wheezing episodes in an additive fashion. In children with asthma, measuring lung function at age 5 years added little to the medical history for predicting future wheezing episodes through age 12 years.

Conclusions: In high-risk urban children, age-related trajectories of allergic sensitization were not associated with lung function development; however, both indicators were related to continued wheezing. These results underscore the importance of understanding early-life factors that negatively affect lung development and suggest that treating allergic sensitization may not alter lung function development in early to mid-childhood.

Keywords: Childhood asthma; allergic sensitization; impulse oscillometry; lung function; spirometry.

Figure 1.. Intraclass correlation coefficient throughout the ages of 5 to 12 years for lung function measurements with spirometry and IOS.

The symbols represent the ICC for unadjusted data or data adjusted for predicted total lung capacity. Abbreviations: FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; FEF_25–75, forced expiratory flow at 25–75% of FVC; IOS, impulse oscillometry; AX, area of reactance; R5, resistance at 5 Hz; R10, resistance at 10 Hz; X5, reactance at 5 Hz.

Figure 2.. Childhood allergy trajectories and age-related trends in FEV₁/FVC ratio and AX.

Longitudinal trajectories of allergy sensitization in the URECA cohort through age 10 years were compared to age-related changes in lung function from age 5 years to 12 years. The panels show the association between sIgE trajectories and FEV₁/FVC ratio (A) or AX (C), between skin test trajectories and FEV₁/FVC (B) ratio or AX (D).

Figure 3.. Relationships between lung function, trajectories of allergic sensitization, and wheezing episodes.

Lung function was measured yearly from ages 5–12 years, AX was adjusted for predicted TLC, and average values were calculated and compared to the sum of wheezing illnesses during the same time intervals. Similarly, allergy trajectories derived from multiple measurements through age 10 years were compared to the sum of wheezing illnesses. The lines represent the smoothed trend line with 95% confidence intervals. Correlations of association between sum of wheezing episodes with average values of FEV₁/FVC (A), and of AX (C). Correlations of association between median for sum of wheezing episodes with skin test trajectories (B), and sIgE trajectories (D).

Figure 4.. Allergic sensitization trajectories with wheeze and FEV₁/FVC ratio or AX.

Children were categorized by trajectories of allergic sensitization (serum allergen-specific IgE), and relationships between lung function (average Z-score, ages 5–10 years) and wheezing illnesses (sum, age 5–10 years) were plotted. The smoothed trend lines and 95% confidence intervals are displayed.

Figure 5.. Independent effects of predictors at age 5 years on future wheezing episodes in children with asthma.

The number of wheezing episodes were summed up from the two years before the 5-year clinic visit. The number of positive skin tests and AX and FEV₁/FVC was assessed at age 5. Each factor was analyzed as a predictive factor for wheezing episodes at age 6 to 10 (left) or at age 11 to 12 (right).