[Age-related decline in forced expiratory volume in one second and forced vital capacity based on a longitudinal observation of Japanese males].

Forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) of 243 healthy male Japanese workers were measured on as annual basis over seven years, and their longitudinal decline was compared with the age coefficient of cross-sectional prediction equations reported previously for Japanese adults. In this study, a man, assumed to be 1.65 meter tall, was expected to have a respective 22 ml and 11 ml decline annually in FEV1 and FVC. Age-related differences of those indices obtained from cross-sectional prediction equations, however, ranged from 22 ml to 31 ml a year in FEV1 and from 16 ml to 25 ml in FVC for men of the same height. Furthermore, in those equations, age was simply employed as a first-order explanatory variable for ages ranging from the later teens to over sixties, although age-related acceleration of FVC decline is suggested in this study. These results indicate that evaluations of measurements relating to time-series pulmonary functions on cross-sectional prediction equations might be biased. This is probably due to the influence of age-cohort. It seems necessary to build up the reference standards for longitudinal pulmonary function change for an appropriate evaluation of time-series data of FVC and EFV1.