Background Patients with chronic obstructive pulmonary disease (COPD) may have impaired pulmonary function before reaching FEV1/FVC<0.7, and the characteristics of impaired pulmonary function are still unclear. There are few relevant studies at present.
Objective To compare the differences of lung function indexes between smokers and non-smokers with FEV1/FVC≥0.7, and explore the characteristics and influencing factors of lung function impairment in smokers with FEV1/FVC≥0.7, so as to provide evidence for early identification of COPD.
Methods Totally 388 smokers (smoking index: more than 50) and non-smokers who underwent pulmonary function examination in our hospital from March 2017 to April 2020 were studied retrospectively (including 223 males and 165 females). These included patients did not have chronic airway disease and their lung function showed FEV1/FVC ≥ 0.7. According to age, they were divided into younger than 50 years old group (n=86), 50-70 years old group (n=197) and more than 70 years old group (n=105). The pulmonary function indexes of smokers and non-smokers in each group were compared and analyzed. Statistical analysis was carried out on the influencing factors of each pulmonary function index in this population.
Results In the younger than 50 years old group, the lung function volume indexes FVCpred% and ICpred% of smokers were significantly lower than those of non-smokers (P=0.041, P=0.043). In the 50-70 years old group, the flow rate indexes FEV1pred%, FEV1 / FVC, the volume indexes FVC, FVCpred% and ICpred% of smokers were lower than those of non-smokers (P<0.05). In the older than 70 years old group, the FVCpred%, FEV1pred% and IC pred% of smokers were lower than those of non-smokers (P<0.05). Nine linear regression analyses were performed on the smokers population with lung function indexes as dependent variables and gender, age and smoking index as independent variables. The results showed that the influencing factors of FVC included gender (B=-0.756, 95% CI:-1.079 to -0.432), age (B=-0.032, 95% CI: -0.040 to -0.025) and smoking index (B=-0.001, 95% CI: -0.001 to 0.000); the influencing factors of FEV1 included gender (B=-0.586, 95% CI: -0.840 to -0.333), age (B=-0.028, 95% CI: -0.034 to -0.022) and smoking index (B=-0.001, 95% CI: -0.001 to 0.000); The influencing factors of IC included gender (B=-0.530, 95% CI: -0.814 to -0.247), age (B=-0.018, 95% CI: -0.025 to -0.011) and smoking index (B=-0.001, 95% CI: -0.001 to 0.000). Among the lung function indexes, FVC pred% (B=-0.027, 95% CI:-0.034 to -0.020), FEV1 pred% (B=-0.028, 95% CI: -0.034 to -0.022) and IC pred% (B=-0.033, 95%CI: -0.041 to -0.025) were affected only by smoking index. RV was only affected by age (B=0.013, 95%CI: 0.003 to 0.024), while FEV1/FVC and RV pred% was almost not affected by gender, age or smoking index.
Conclusion Among smokers with FEV1/FVC ≥ 0.7, the impairment of smoking to lung function can be found in all age groups. However, in the young population of < 50 years old group, the decline of FVC pred% and IC pred% were more obvious. The decline of volume indexes in the early impairment of lung function induced by smoking need to be paid more attention.
DownLoad: