Lean body mass is positively associated with lung function at age 15

Abstract

Conflicting results exist for the association between overweight/obesity and lung function in children/adolescents, possibly because BMI cannot distinguish between fat mass and lean body mass. We assessed associations between body composition developmental trajectories from 7 to 15 years, and lung function at 15 years in the ALSPAC birth cohort (n=2116). FVC and FEV 1 were measured at age 15 years using spirometry. BMI and DXA-measured body composition were assessed between 7-15 years, and used to calculate fat mass index (FMI) and lean body mass index (LBMI) by dividing the respective measures by height 2 . Developmental trajectory groups for BMI, LBMI, and FMI were identified using group-based trajectory modeling. Associations between these groups and lung function were assessed using multivariable linear regression models adjusted for sex, breastfeeding, birth weight, gestational age, total energy intake, current smoking status of the child and maternal smoking during pregnancy. BMI and FMI models were also adjusted by LBMI groups, and the LBMI model was adjusted by BMI groups. Four parallel trajectory groups were identified for BMI and LBMI, and three for FMI. Compared to the group with persistent low LBMI, those with higher LBMI during development had higher FVC (0.21L, 95%CI [0.13-0.29], 0.56 [0.45-0.67], 0.87 [0.71-1.03] for the three groups in increasing order of LBMI, respectively). The same was observed for FEV 1 , and after stratifying by sex and excluding asthmatics. BMI and FMI trajectory groups were not associated with FVC or FEV 1 . LBMI was positively associated with lung function in 15 year olds, and may be a better marker than BMI of body composition in adolescents. Funding: ALEC (EU H2020 Grant #633212).