Spirometric studies in Malaysians between 13 and 69 years of age.

Spirometry was performed on 1,999 subjects (1,385 males and 614 females) ranging in age from 13 to 69 years and comprising of all the main races in Malaysia. They were divided into 6 age groups. Mean forced vital capacity (FVC) in the males and females was 3.49 +/- 0.02 L and 2.51 +/- 0.02 L respectively. Both FVC and FEV1 correlated negatively with age. Regression analysis on data between the ages of 20 to 69 years revealed an age-related decline in FVC of about 30 ml per year of life in the males and 22 ml per year in the females. Multiple stepwise regression of the data for the prediction of an individual's FVC above the age of 20 years gave an equation for the males: FVC = 0.0407 (height)-0.0296 (age)-2.343 L and for the females: FVC = 0.031 (height)-0.022 (age)-1.64 L. Predicted FVC values derived from equations based on other populations were considerably higher than the observed mean in this study, re-emphasizing the need to be cautious when applying formulae derived from one population to another. Grossly erroneous conclusions may be reached unless predicted equations for lung-function tests for a given population group are derived from studies based upon the same population group.