Early infancy BMI trajectories and lung function and asthma during childhood

Abstract

Previous studies assessing the association of birthweight and infant weight gain with lung function and asthma have focused on the difference between two time points or on growth patterns. Body mass index (BMI) trajectories, which integrate information on multiple aspects of growth, may allow a more accurate identification of children at higher risk of future respiratory diseases. We assessed the associations of BMI trajectories from birth to 4 years with lung function and current asthma at 7 years. We included 1399 participants from the population-based INMA birth cohort study. Five BMI trajectories were previously identified: ‘average birth size-slower BMI gain’, ‘higher birth size-accelerated BMI gain’, ‘higher birth size-slower BMI gain’, ‘lower birth size-accelerated BMI gain’ and ‘lower birth size-slower BMI gain’. At 7 years, lung function (FVC, FEV1, FEV1/FVC) was assessed by spirometry and current asthma was assessed by questionnaire. After adjustment for potential confounders, children in the accelerated BMI gain trajectories had higher FVC at 7 years either if they departed from lower (37mL; 95%CI: -1.2 to 75) or higher (51mL; 13 to 90) birth size, compared to children in the ‘average birth size-slower BMI gain’ trajectory. These two groups also presented lower FEV1/FVC at 7 years, although the associations were not statistically significant. Children in the ‘low birth size-slower BMI gain’ trajectory had -47mL (95%CI: -84 to -11) lower FVC at 7 years, compared to children in the ‘average birth size-slower BMI gain’ trajectory. No associations were observed for FEV1 or asthma. Early infancy BMI trajectories can identify adverse growth patterns associated with future poorer respiratory health.