Body mass index trajectories from birth to early adulthood and lung function development

Background: Few studies have investigated the influence of body mass index (BMI) trajectories on lung function covering the entire growth period.

Methods: We conducted a prospective study using data from the Swedish BAMSE birth cohort. Latent class mixture modelling was employed to examine the diversity in BMI z-scores from birth to 24 years of age. Participants with four or more BMI z-scores were included (n=3204, 78.4%). Pre-bronchodilator spirometry was tested at 8, 16 and 24 years, while post-bronchodilator spirometry, multiple-breath nitrogen washout (for lung clearance index) and urinary metabolomics data were assessed at 24 years.

Results: Six distinct BMI development groups were identified. Compared to the stable normal BMI group, the accelerated increasing BMI group exhibited reduced pre- and post-bronchodilator forced expiratory volume in 1 s (FEV₁)/forced vital capacity (FVC) ratio z-scores (pre: β= -0.26, 95% CI -0.44- -0.08; post: β= -0.22, 95% CI -0.39- -0.05), along with elevated lung clearance index (0.30, 95% CI 0.22-0.42) at 24 years. The persistent high BMI group demonstrated lower FEV₁ (-0.24, 95% CI -0.42- -0.05) and FVC (-0.27, 95% CI -0.45- -0.01) z-score growth between 16 and 24 years, and elevated lung clearance index (0.20, 95% CI 0.03-0.39) at 24 years. However, those impairments were not observed in the accelerated resolving BMI group. Conversely, the persistent low BMI group displayed persistently decreased FEV₁ and FVC from 8 to 24 years, as well as decreased lung function growth. Additionally, histidine-related metabolites were associated with pre- and post-bronchodilator FEV₁ (hypergeometric false discovery rate=0.008 and <0.001, respectively).

Conclusions: Early interventions aiming for normal BMI during childhood may contribute to improved lung health later in life.