Twelve-year Cumulative Incidence of Airflow Obstruction among Japanese Males

Background To date, there is very limited longitudinal data on COPD and incidence estimates in Japan. The aim of this study was to investigate the 12-year cumulative incidence of airflow obstruction (COPD) in Japanese males. Methods This study included 913 male subjects, aged 30-76 years, who underwent lung function tests at a medical check-up in 1994 (baseline), 1999, and 2006. The study group consisted of 263 persistent never smokers, 296 early quitters, 117 late quitters, and 237 persistent smokers without airflow obstruction at baseline. The 12-year cumulative incidence of airflow obstruction was estimated. The spirometric criteria for diagnosis of airflow obstruction were forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) of <0.7 and 5th percentile lower limit of normal (FEV1/FVCcumulative incidences of airflow obstruction using fixed criteria and LLN criteria were 5.3%, 7.6% in persistent never smokers, 10.5%, 10.1% in early quitters, 12.0%, 14.5% in late quitters, 13.5%, 17.3% in persistent smokers, respectively. In logistic regression models, the odds ratio (OR) of developing airflow obstruction defined using the fixed criteria and the LLN criteria increased with a history of smoking status and increasing pack-years of smoking. When using the LLN criteria to define obstruction compared with fixed criteria, higher incidence rates among aged <60 and lower incidence rates among aged ≥60 were observed. Conclusion The cumulative incidence of airflow obstruction defined using the fixed ratio and LLN criteria was strongly associated with smoking status. This study suggested that early cessation of smoking may prevent the development of airflow obstruction among smokers.