Determinants of adolescent lung function in Indians: race, nutrition and systemic inflammation

RationaleWhile determining normal variation of spirometric volumes, the geo-political construct of Indian inadequately captures the diverse racial structure and varied lifestyles that exist for 1 in 5 people globally. It is necessary to determine the degree of racial heterogeneity and other underlying factors to know whether lower spirometric volumes of Indians is normal or abnormal. ObjectivesTo investigate the differences in spirometric volumes and their associations with overall health parameters, for adolescent children and young adults, across geo-ethnic regions within India. MethodsData was analyzed for 2338 healthy subjects aged 9-19 years with acceptable spirometry from SOLID cohort. Associations between lung function and potential determinants (Race, anthropometry, nutrition, family/life history, airway oscillometric parameters and systemic inflammation) were examined by using multiple regression. Latent profile analysis (LPA) was performed for 903 subjects to uncover hidden sub-phenotypes. ResultsFEV1 and FVC varied significantly between Indian genetic ancestries, being highest in Tibeto-Burmans and lowest in Dravidians. After statistical adjustments, FEV1 and FVC were positively correlated with waist-height-ratio, shoulder-height-ratio, normalized BMI, and blood hemoglobin. Lower FVC was associated with lower expiratory flows (PEF and FEF25-75), higher lung reactance (X5), higher airway resistance (R10 and R15), gastro-intestinal symptoms, and higher inflammation (IL-8 and IL-17). A sub-phenotype of thinness, higher inflammation (IFN-gamma, IL-17, TNF-alpha, IL-8) and lower FVC was identified on LPA for 35% of the sample. ConclusionsSpirometric volumes in Indians are different between major racial subgroups but may also be abnormally low due to prevalent nutritional or environmental adversity. Care must be taken while establishing normative standards.