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

Background: Limited studies have explored the impact of body mass index (BMI) on lung function covering the entire lung growth period. Methods: A prospective study was conducted based on data from the Swedish BAMSE cohort (N=4089). Latent class growth mixture modeling was used to explore the heterogeneity in the BMI z-scores from birth to 24 years of age (up to 14 time points). Pre-bronchodilator (BD) spirometry was tested at 8, 16, and 24 years, and post-BD spirometry and multiple-breath nitrogen washout (for lung clearance index, LCI) were tested at 24 years. Results: The current study included 3178 participants (77.7%). Six discernible BMI trajectories from birth through early adulthood were identified. Compared to participants in the stable normal group, participants with higher BMI levels demonstrated increased pre-BD FVC z scores at 8, 16, and 24 years of age. Conversely, those in the persistent low BMI group exhibited decreased pre-BD FEV1 and FVC z scores at 8, 16, and 24 years, as well as post-BD FEV1 and FVC z scores (β=-0.26, 95% CI=[-0.39, -0.14], and -0.29, [-0.41, -0.16], respectively) at 24 years. We observed a reduction in post-BD FEV1/FVC ratio z scores in the accelerated increasing BMI group (-0.25, [-0.42, -0.07]), along with increased LCI in both the persistent high and accelerated increasing BMI groups at 24 years. Conclusions: In our cohort, the persistent high and accelerated increasing BMI groups were associated with obstructive lung function pattern and small airway dysfunction. Having a persistently low BMI was associated with a restrictive pattern. Thus, maintenance of normal somatic growth patterns may lead to improved lung health during childhood.