Application of the COOP/WONCA charts to aged patients with chronic obstructive pulmonary disease: a comparison between Japanese and Chinese populations

BACKGROUND The prevalence of chronic obstructive pulmonary disease (COPD) is similar in Japan and China and is increasing due to high rates of smoking in these countries. Reducing COPD is an important public health issue. The goals of this study were to verify the reliability and validity of the Japanese version of the COOP/WONCA charts, a tool for measuring health status, and to examine the qualitative differences in health status between Japanese and Chinese patients with COPD and between these patients and healthy subjects. METHODS From 2008 to 2011, we examined the factors affecting the health status of Japanese and Chinese populations living in six cities. Participants were patients with COPD staged according to the Global Initiative for Chronic Obstructive Lung Disease (GOLD) criteria (140 Japanese, 201 Chinese) and healthy subjects (243 Japanese, 199 Chinese), all 50 to 79 years old. Health status was measured by using the COOP/WONCA charts, and basic information such as smoking status and medical history was reported by the participants. RESULTS The Japanese and Chinese versions of the COOP/WONCA charts were shown to be reliable and valid by test-retest, comparison with the SF-36 and respiratory symptoms, and correlation of results obtained from patients and their physicians. Stepwise multiple regression analyses demonstrated that "Physical fitness", "Daily activities", and "Social activities" were predicted by COPD status and/or respiratory symptoms; "Feelings" by nationality and respiratory symptoms; "Pain" by sex and respiratory symptoms; and "Overall health" by nationality. When the COOP/WONCA scores were stratified by nationality, age, sex, and COPD status, the difference of each score between the patients and healthy subjects was larger for the Chinese subjects than for the Japanese. The physical, psychosocial activities, and pain scores increased significantly as COPD status worsened in Chinese subjects, whereas these scores were not affected by sex, age, or COPD status for Japanese subjects. Brinkman index and use of smoky fuel indoors affected the COOP/WONCA scores in Chinese patients but not in Japanese patients. CONCLUSIONS The Japanese COOP/WONCA charts are reliable and valid. COPD more severely affected the health status of Chinese participants than of Japanese participants. These results suggest that countermeasures against insufficient health care and smoky environments may improve the health status of Chinese patients with COPD.