Normal reference value of forced vital capacity of Chinese younger men and geographical factors.

Objective This paper aims at supplying a scientific basis for unifying the normal reference value standard forced vital capacity of Chinese younger men. Methods The research is made to study the relationship between the normal reference value of 25,393 examples of forced vital capacity of younger men and eight geographical factors in 304 areas in China. Results It is found that the correlation of geographical factors and the normal reference value of forced vital capacity of younger men is quite significant (F = 84.831, P = 0.000). By adopting the methods of mathematical regression analysis, one regression equation is inferred; Y = 5.404 + 0.0002371X1 - 0.001258X2 + 0.04169X3 + 0.01843X4 - 0.01981X6 + 0.2200X8 ± 0.418, in the above equation, Y is the normal reference value of forced vital capacity of younger men (L); X1 is the altitude (m); X2 is the annual sunshine duration (h); X3 is the annual percentage of sunshine duration (%); X4 is the annual mean air temperature °C); X6 is the annual mean relative humidity (%); X8 is the annual mean wind speed (m/s); 0.418 is the value of the residual standard deviations. Conclusion If geographical values are obtained in a certain area, the normal reference value of forced vital capacity of younger men in this area can be reckoned by using the regression equation. Furthermore, according to the geographical factors, China can be divided into eight districts; Northeast China District, North China District, Shanxi-Shaanxi-Inner Mongolia District, Middle and lower reaches of the Changjiang River District, Southeast Chine District, Northwest China District and Southwest China District and Qinghai-Tibet Plateau District. [ABSTRACT FROM AUTHOR]