Narrative review of current COPD status in Japan

Abstract

Chronic obstructive pulmonary disease (COPD) causes morbidity and mortality worldwide. Due to the improvement in environmental sanitation and medical care, the general life span has increased in the past decades in Japan. However, many older patients with COPD develop a wide range of comorbidities, and the impairments in the activities of daily living result in frailty and increase social and economic burdens. Population-based studies have shown that the prevalence of COPD is approximately 10% among subjects aged ≥40 years, but more than 80% of COPD patients are underdiagnosed. The Ministry of Health, Labour, and Welfare in Japan proposed the National Health Promotion in the 21st century, termed Health Japan 21 (the second term), in 2013 to prevent the onset and progression of noncommunicable diseases (NCDs), including COPD. The government, medical society, and community have been attempting to increase the recognition of COPD and promote smoking cessation. Additionally, Japanese cohorts have revealed distinct clinical features in Japanese patients with COPD, including lower rates of patient-reported exacerbations, less frequent coexisting cardiovascular disease and metabolic syndrome, and lower use of inhaled corticosteroids in Japan compared to the Western countries. Moreover, the poor adherence to inhaled medications is found in approximately 20% of subjects, and rehabilitation is performed in 26% of hospitalized patients with COPD. Therefore, more efforts should be made to improve adherence and access to pulmonary rehabilitation. Overall, Japanese COPD patients share common clinical and social features with COPD patients in other countries. Further international corroboration may help establish better comprehensive management of the disease.

Keywords: Chronic obstructive pulmonary disease (COPD); Japan; emphysema; prevalence.

Figure 1

Prevalence and underdiagnosis of COPD in Japan. All data were based on subjects aged ≥40 years. NICE (2), Takahata (3), and Hisayama (5) were conducted with a population-based approach. “Health exam” indicates a study of subjects who underwent comprehensive medical examination including spirometry (7). “Outpatients with CVD” indicates a study of outpatients with cardiovascular disease (CVD) at primary care clinics and performed spirometry (8). “Global data” indicates a meta-analysis of 34 studies including subjects aged ≥40 years (1).

Figure 2

Trend in number of deaths from COPD in Japan. Data were obtained from the nationwide database of the Ministry of Health, Labour, and Welfare in Japan.

Figure 3

Causes of death in patients with COPD from Japanese and international studies. The Hokkaido COPD cohort (25) and Kyoto University cohort (26) were conducted at hospitals, and forced expiratory volume in 1 sec (FEV1) was approximately 60% (% predicted). The Takahata study (27) was a population-based study in which subjects with airflow limitation were included, but the severity of airflow limitation was mild (mean FEV1 was over 90% of predicted). IMPACT (28) was an international multicentre interventional study conducted in the United States, Europe, and Asia.

Figure 4

Use of ICSs and LAMAs prior to enrolment in international interventional studies. DYNAGITO (41,42), IMACT (43,44), KRONOS (45,46), and SHINE (47,48) studies were conducted all over the world, including in the United States, Europe, Asia, and Japan. The use of inhaled corticosteroids (ICSs) and long-acting muscarinic antagonists (LAMAs) was compared between a subset of the Japanese population and the whole data set.