[Predicted vales of respiratory function tests in young Japanese aged from 10 to 20 years]

To find predicted values of respiratory function tests in young persons in Japan, we measured slow vital capacity and forced vital capacity in 1,141 subjects aged from 10 to 20 years. The values obtained from 636 persons (363 males and 273 females) who were not smokers or had no suspected rhinitis or asthma were analyzed. Although FEV1% by the Gaensler and Tiffeneau methods were almost constant regardless of age, all other values of respiratory function tests increased with age and then reached a plateau level in late teens. Excluding the Gaensler and Tiffeneau FEV1%, in a single regression analysis using gender, age, and height, both the contribution ratio and regression coefficient were the highest using height, followed by age. In addition, the result was similar with multiple regression analysis. Therefore, for a young person aged from 10 to 20 years, body height is the most important predictor variable of respiratory function tests, compared to gender and age. For each respiratory function test, we showed the prediction relation according to gender obtained from multiple linear regression analysis using 2 variables of height and age.