To investigate the relationship between pulmonary function and smoking status in patients with preserved-ratio impaired spirometry (PRISm) and chronic obstructive pulmonary disease (COPD) over 40 years of age in Shijingshan district of Beijing.

Data were obtained from people over 40 years old in Shijingshan district of Beijing who underwent lung function screening from June to December 2019. According to lung function measurements, 477 patients were diagnosed with PRISm and 416 had COPD. They were divided into a non-smoking group, a past smoking group, and a current smoking group according to current smoking status, and the lung function was compared among the three groups.

Among the 416 COPD patients, 62.5% were male and 37.5% were female, while 56.4% of PRISm patients were male and 43.6% were female. Changes in the lung function-related indexes FEV1/FVC and FEV1%pred were closely related to current smoking status, but had no statistically significant association with passive smoking status. The number of patients who had smoking cessation was significantly higher than that of those who were still smoking according to their current smoking status. Correlation analysis showed that the number of years of smoking and the amount of cigarettes smoked in patients with COPD were strongly correlated with lung function decline (P<0.05), and FEV1/FVC was negatively correlated with the number of years of smoking cessation.

Smoking status is closely related to the change in lung function in Chinese people with COPD. Early screening of the population by pulmonary function testing and early intervention and follow-up according to their smoking status are beneficial to reduce the incidence of COPD.