Effect of smoking status on spirometric lung age in adult Chinese Men

Smoking is one of the most unhealthy behaviours and responsible for a variety of respiratory diseases. Although spirometric lung age (SLA) is regarded as an effective way to augment the smoking quit rate in other countries, it has not been calculated in Chinese smokers. Thus, the aim of this study was to determine the association of SLA with smoking status, and further explore whether smoking duration, dependence and other factors such as obesity and physical exercise affect SLA in Chinese current smokers. A total of 431 healthy men aged 20 years and older took part in the study from September 2018 to August 2019. Spirometric test was measured through a portable spirometry, and smoking status including smoking duration and dependence was investigated by using a questionnaire. SLA was calculated from an established equation which is based on the inverse calculation of the forced expiratory volume in one second in the Chinese population. Lung age difference (∆LA) could be obtained by counting the difference between SLA and chronological age. Results indicated that ∆LA is remarkably higher in current smokers than that in ex-smokers and non-smokers (p < 0.01). The study also revealed that smoking duration and dependence are related to ∆LA. Smokers with long smoking duration (smoked ≥10 years) and high dependence (consumed ≥20 cigarettes per day) had a significantly higher ∆LA than their counterparties (p < 0.01). Multiple regression analysis showed that body mass index, smoking duration and cigarettes per day were independently correlated with ∆LA in the current smokers (p < 0.01). The findings suggest that not only smoking or not, but smoking duration, dependence and obesity are strongly associated with SLA.