Parameter estimated by multiple linear regression analysis models for FEV1/FVC and FEV25–75%/FVC as dependent variables and sex, age class, presence/ absence of personal history of respiratory symptoms, height, and weight as independent variables.

aThis parameter is set to zero because it is redundant*β coefficients indicate how much a dependent variable changes per each unit variation of the independent variable, taking into account the effect of the other independent variables in the model. For categorical variables, β coefficients represent the effect of moving from the “reference” category (a) to anotherData are shown for the overall sample of 3,200 children.Parameter estimated by multiple linear regression analysis models for FEV1/FVC and FEV25–75%/FVC as dependent variables and sex, age class, presence/ absence of personal history of respiratory symptoms, height, and weight as independent variables.