Abstract
Objective: To investigate the effect of smoking on respiratory functions from health check-up data and determine a smoking index cutoff point encouraging people to stop smoking, with particular focus on analysis regarding smoking amount and gender differences.
Methods: Our subjects were 32,544 persons with analyzable data among 34,383 health check-up examinees at Omiya City Clinic from January to December 2016. By smoking history, they were divided into 3 groups: current smoker group, former smoker group and never smoker group and the mean FEV1/FVC, %FEV1 and smoking quantity index for each group were compared between men and women. In addition, we examined the prevalence of subjects with obstructive impairment among subjects with FEV1/FVC less than 70% as well as an optimal cutoff point for the smoking quantity index for subjects with obstructive impairment.
Results: Significant differences in FEV1/FVC were observed among all 3 groups. For %FEV1, while no significant difference was found between the former smoker and never smoker group in women, significant differences were found for all other comparisons. The smoking quantity index was significantly higher in men than in women for both the smoker and former smoker groups. The optimal smoking quantity index cutoff point for subjects with obstructive impairment was 11.33 pack-years overall and 12.13 pack-years for men but a high cutoff point with predictive value for women could not be determined. The overall prevalence of obstructive impairment was 1.78%. The prevalence of obstructive impairment was 4.22% for the smoker group, 2.66% for the former smoker group and 1.11% for the never smoker group in men and 1.57%, 0.68% and 0.59% in women, respectively, so it was lower in women.
Conclusion: For male current smokers with a smoking quantity index of 12 pack-years or greater, education regarding COPD and actively instructing them to cease smoking were considered to be particularly important. Suggested reasons for the lower prevalence of obstructive impairment in women than in men are the lower smoking quantity index in women and the possibility that the effect of smoking on respiratory function differs between men and women.
