To observe the effect of smoking status on lung function in Chinese people >40 years of age by a 2-year longitudinal follow-up.

This study prospectively investigated 2 682 cases of pulmonary ventilation function, smoking status, regularity of residents drug combination and gender, age, height, weight and other information, observation time for two years, 2 290 people (85.4%) complete the follow-up study.

Of the 2 290 people, 1 197 people (52.3%) are never-smokers, 467 people (20.4%) are ex-smokers, 626 people (27.3%) are current smokers.There were statistically significant differences in the number of age, sex, BMI, lung function COPD and combination therapy among the three groups.After 2 years of follow-up, results show that the lung function FEV₁, FEV₁ % pred, FVC, FEV₁ / FVC showed decreased year by year.After adjusted the difference variables, It showed that, to compared with never smokers, ex-smokers significantly reduced lung function FEV₁, FEV₁ %pred and FEV₁ / FVC, P values were 0.030, 0.011 and <0.001, current smokers significantly reduced lung function FEV₁/FVC.

Never-smokers have the slowest decline in lung function, We advocate non smoking or smoking as early as possible.

Smoking; Lung function; Chronic obstructive pulmonary disease