To assess anual change in lung function, if possible, we have to observe individual anual change and put together to investigate standard anual change for the whole subjects. We selected healthy subjects who took general health examination ten times for about ten years. They did not have any signs and symptoms, smoked less than ten cigarettes a day, had no past history of lung diseases and no abnormality was detected on their chest X-ray. The subjects were all male, 20 cases who took the first examination in their 3 decades, 20 cases who took the first examination in their 4 decades and 12 cases who took the first examination in their 5 decades. FVC, FEV_1.0, FEV_1.0% and Peak flow rate were analyzed. Linear regression line for the whole subjects was calculated only by the first examination data. Next, we calculated linear regression line for every one case, got the average slope and intercept of these lines and compared with the former regression line. Residual standard deviations of the average of individual regression lines was smaller than those of the regression lines calculated by the only first examination data. And we observed (1) anual decrease in FVC and FEV_1.0 tended to be smaller as the subjects got older (2) anual decreases in FEV_1.0% and Peak flow rate were obscure and this tendency was different from the data calculated by the only first examination data.

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