Abstract
Objective: To investigate variation in lung age with difference in smoking habit and study the usefulness of lung age.
Methods: The subjects were 18,975 men from among 33,052 people who underwent health check-ups at Omiya City Clinic from January to December 2015. Based on their smoking history, subjects were assigned to one of 3 groups: Current Smoker Group, Ex-Smoker Group and Never Smoked Group. and were investigated regarding their age, pulmonary function test results, and chest X-ray findings. Lung age was calculated using the formula stipulated by The Japanese Respiratory Society and a comparative examination carried out according to lung age difference = lung age - real age. We examined temporal changes in lung age difference in subjects who had continuously undergone health check-ups for 20 years.
Results: Lung ages were 61.5 years (±17.4), 61.7 years (±14.7) and 56.2 years (±14.9) in the Current Smoker, Ex-Smoker and Never Smoked Groups, respectively, and lung age differences were +12.7 years (±14.6), +8.9 years (±11.1) and +8.2 years (±12.1), respectively, and the lung age difference was significantly greater in the Current Smoker Group. Also, at 4.4%, the prevalence of emphysematous lesions observed in X-rays in the Current Smoker Group was significantly greater than in the other 2 groups. The lung age difference in the Ex-Smoker Group tended to become smaller. The lung age difference in the Ex-smoker Group tended to become smaller the longer the period since stopping smoking. While there had been no significant difference in lung age among the 3 groups 20 years ago, at the time of the study, lung age in the current smokers was higher and the lung age difference was significantly greater. No significant difference was observed between the Ex-Smoker and Never Smoked Groups.
Conclusion: Lung age difference increases due to smoking. It can be decreased by stopping smoking and is an indicator that is well correlated with smoking habit. The effect of stopping smoking at an early date is soon reflected as a change in lung age and as it is readily available to the examinee, lung age is effective in the early discovery and prevention of COPD.
