Prevalence of airflow limitation on medical check-up in Japanese subjects.

The prevalence and mortality of chronic obstructive pulmonary disease (COPD) is expected to increase in the future throughout the world. Little data is available on the prevalence of airflow limitation in Japan, especially on medical check-up. The purpose of this study was to assess the prevalence of airflow limitation in Japanese subjects during medical check-ups. The study subjects were 13,534 Japanese subjects (8,583 males and 4,951 females) aged 40-69 years who underwent medical check-ups at the Japanese Red Cross Kumamoto Health Care Center. Pulmonary function data were analyzed according to smoking habits in each age group. The spirometric criteria for diagnosis of airflow limitation were forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) < 70%. The severity of COPD was defined according to the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines. People with a medical diagnosis of asthma or individuals who had other pulmonary diseases were excluded from a diagnosis of COPD. The prevalence of airflow limitation was 7.0% in all subjects, 9.1% in males and 3.3% in females. Using the GOLD system, the prevalence of mild, moderate, severe and very severe airflow limitation was 7.06, 1.92, 0.10 and 0.00%, respectively, in males. In females, the prevalence of mild, moderate, severe and very severe airflow limitation was 2.67, 0.63, 0.02 and 0.00%, respectively. Only 10 cases with airflow limitation reported a previous diagnosis of COPD. These results suggest that screening spirometry during medical check-ups can identify many COPD patients not aware of this disease and highlight the need for enhanced screening efforts, intervention and treatment.