Changing relationship between FEV1 and height during adolescence.

Forced expired volume in one second (FEV1), body weight, standing and sitting height, and chest dimensions were measured in 962 male and 674 female subjects aged between 9 and 20 years. Standing height and body weight correlated best with ventilatory indices in boys. In girls, standing height, body weight and chest circumference correlated more or less equally with ventilatory indices. Regression analysis of logarithmically transformed FEV1 on standing height were done. In the boys, the correlation coefficient between In FEV1 and in height increased from 0.34 at 9 years to 0.77 at 13 years of age, while girls appear to have reached a peak by 12 years of age. The mean allometric constant was 3.109 and 3.032 for male and female subjects respectively. However, age-specific allometric constants increased in the boys from 2.846 to a peak value of 4.045 at 16 years of age. In the girls, the constant increased to a peak value of 4.5 a year earlier than in boys. The log-log plot of FEV1 against standing height was nonlinear, becoming more curvilinear with increasing height. These findings reflect changes in body proportions and shape during adolescence with lung growth lagging behind growth in standing height.