Thinness negatively affects lung function among Sri Lankan children

There have been conflicting findings on the effect of body mass index (BMI) on lung functions in children. Therefore, we studied the relationship between spirometry parameters and BMI among healthy Sri Lankan school children aged 5-7 years. A cross-sectional study was conducted among 296 school children (5-7-year-old) without apparent lung disease. Recruitment was done with stratified random sampling. Spirometry parameters, FEV.sub.1, FVC, PEFR, and FEV.sub.1 /FVC ratio were determined. The acceptable and reproducible spirometry recordings were included in the analysis. Simple and multivariate linear regression analysis examined possible associations of lung function parameters with BMI, socio-demographic variables and indoor risk factors. Also, the mediator effect of gender on lung function through BMI was explored. The participants' mean age (SD) was 6.4 (0.65) years. One-third were thin/severely thin (37%). A statistically significant difference in FVC (p = 0.001) and FEV.sub.1 (p = 0.001) was observed between BMI groups (obesity/overweight, normal, and thinness). Yet, PEFR or FEV.sub.1 /FVC did not significantly differ among BMI groups (p = 0.23 and p = 0.84). Multivariate regression analysis showed that FEV.sub.1 and FVC were significantly associated with BMI, child's age, gender, family income, father's education, having a pet, and exposure to mosquito coil smoke. Interaction between gender and BMI for lung functions was not significant. The thin children had significantly lower FVC (OR: -0.04, 95%CI: -0.077, -0.012, p = 0.008) and FEV.sub.1 (OR: -0.04, 95%CI: -0.075, -0.014, p = 0.004) than normal/overweight/obese children. Family income demonstrated the greatest effect on lung functions; FVC and FEV.sub.1 were 0.25L and 0.23L smaller in low-income than the high-income families. Lower lung function parameters (FVC and FEV.sub.1) are associated with thinness than normal/overweight/obese dimensions among children without apparent lung disease. It informs that appropriate nutritional intervention may play a role in improving respiratory health.