To the best of our knowledge, this study provided the most comprehensive and latest assessment of the burden of COPD in China. The standardized methods used in the GBD study made it possible to compare the COPD burden in China with that at the global level. From 1990 to 2019, the ASRs of COPD burden, especially mortality and DALYs, have been dramatically decreased. This decline was mainly attributed to the rapid socioeconomic development in China during the past three decades as a result of better nutrition supply, living conditions, education, and health care, which can effectively reduce the risk of chronic diseases. However, the absolute number of COPD incidence and prevalence have an increasing trend with a nearly two-thirds increment in 2019 than in 1990, which was contrary to the variation in the corresponding ASRs. According to the GBD estimates, China represented 24% of all new diagnosis, 21% of all prevalent cases, 32% of all deaths, and 27% of all DALYs from COPD across the world in 2019.12 Why does China have such a heavy burden of COPD? One major reason for the rise of COPD is population aging. Whereas there were 13 million Chinese residents older than 70 years in 1970, it has climbed to over 80 million now and will be 215 million by 2050.16 Other potential reason is cigarette smoking. According to a cross-section study recruited more than 60,000 adults aged over 40 years across all major provinces in China, it astonishingly found that 58% of the male participants were smokers, whereas only 4% of female participants have the experience of smoking.17 As COPD contributes to an immense economic burden, as well as a considerable impairment on physiological function and quality of life of patients, our study highlighted that COPD continues to cause a heavy burden on patients, the health-care system, and society in China that call for aggressive preventive measures and management strategies to defeat COPD in China.
Despite decrease in age-standardised rates of COPD burden, China still has substantially higher COPD burden in mortality and DALYs than the global average. This high rate of health loss from COPD might be the result of its relatively late diagnosis and management.18 Evidence suggests that COPD is underdiagnosed in China partly due to diagnosis is often based on symptoms rather than spirometry.19 Asymptomatic patients are often late in seeking care and do not ask for medical care until the symptoms interfere with their daily life. Notably, asymptomatic patients who are in urgent need for early diagnosis account for a considerable proportion (35.1%) of all COPD patients, which represents a major challenge in China.20 Physicians should be trained and community health-care centers should be provided with spirometers to help early diagnose COPD patients in high-risk population, such as those with chronic sputum production or dyspnea, or heavy smokers.
In view of the relationship between the COPD burden and age, our data confirms that COPD is a progressive disease. The COPD burden dramatically increased with age, and reached a peak at the age group of older than 95 years. This increase was most prominent in middle aged and older populations. The primary drivers of this increase were longer life expectancy in China and continuous exposure to risk factors, such as indoor and outdoor pollution. However, it was important to note that COPD can also be present early in life. Wang et al. showed that the prevalence of COPD was 2.1% among the young adults aged 20–39 years in China.21 Therefore, young populations should be included in COPD screening programs.
Despite the decrease of premature death caused by COPD, YLD increased significantly, and the proportion of YLD in DALY increased simultaneously, indicating that the burden of disability caused by COPD is on the rise, which is a lot to do with the limited treatment of advanced disease. Currently, the detection rate of lung function in China is very low.22 Many patients with obvious symptoms of cough and sputum do not receive regular pulmonary function examination, resulting in the delay diagnosis of the disease. When many patients are diagnosed, their respiratory obstruction has reached the moderate to severe level.23 Most patients continue to develop limited motor function, resulting in disability and a serious burden on their families and society. Therefore, the level of early detection should be improved to avoid the disabling disease burden caused by the development of the disease from early to late stage.
The burden of COPD shows substantial heterogeneity in China at the province level, with higher ASRs were observed in the less-developed western provinces, such as Sichuan, Tibet, and Gansu. The variation in COPD burden over time showed the same trend among these provinces, with the least decline in the western provinces. A strongly negative association between COPD burden and socioeconomic development can partly explain this inequality of COPD burden at the provincial level. The low socioeconomic development is associated with poor health awareness, inadequate social support, lack of medical care, poor living environment, and increased exposure to some risk factors, such as smoking and biomass fuels. These factors interact with each other to some extent and directly or indirectly lead to the development of COPD. Even in a well-developed country with an advanced health care system, low socioeconomic status, representing as short length of school education, is associated with a poorer prognosis of COPD.24 Indoor air pollution from the burning of coal and biomass fuels is a major cause of COPD in the developing countries. The use of solid fuels is inversely associated with socioeconomic development, because it is very likely that the home of poor people are places where lung injury caused by smoke from solid fuel. Since the 1990s, China has done a lot in the promotion of clean energy.25 Most developed urban areas have basically used cleaner and more effective electricity or natural gas for cooking and heating. However, in the less developed regions, especially in the western China, the penetration rate of clean energy and indoor ventilation equipment is still low, whereas the utilization of solid fuel is still high, leading to a high exposure to this risk factor of COPD. Studies have showed that the occupational exposure to dust and harmful gas is much higher in the western regions than in the central and eastern regions, which is estimated to be related to the higher distribution of mineral resources in the western China.26 Moreover, the cold climate and low average air humidity in the western provinces, such as Tibet, Qinghai, and Gansu, is strongly associated with the high COPD burden.27 In addition, the low lung function detection rate and treatment rate due to socioeconomic underdevelopment further exacerbate the burden of COPD in these regions. A national survey across seven provinces found that only 30% of COPD patients had been diagnosed with COPD-related respiratory disease, 2.4% had received lung function test, and 7.9% had underwent regular medication in the less developed regions of China.28 Therefore, COPD patients in China still have a large amount of unmet needs in terms of health services.
In 2019, the COPD-related mortality and DALYs attributable to all risk factors have been significantly reduced as compared to those in 1990 for the whole population, but smoking is still the most important risk factor. Notably, ambient particular matter pollution has become the most and second important risk factors in 2019, whereas it only ranked fifth and fourth among all risk factors in 1990 for women and men, respectively. With rapid industrialization, air pollution has become the biggest environmental challenge to public health in China. Growing body of evidence have revealed that increased daily mean PM2.5 and PM10 concentrations were significantly associated with increased COPD prevalence and declined respiratory function.29,30 However, the majority of evidence on the effects of air pollution on COPD in China are based on cross-sectional data. So far, there has been no long-term cohort study of respiratory health and air pollution in China. In Europe, studies have shown that reducing exposure to airborne particulate matters appears to attenuate the decline in lung function caused by the exposure to PM.31 For the past decade, Chinese government has showed its ambition and done a lot in the management of air pollution, which partly contributed to the reduction of COPD burden, and might serve as an example for the developing countries.32
Compared with previous studies on COPD burden in China, the present study showed the following strengths. First, our study analyzed the COPD burden, as measured by incidence, prevalence, mortality, and DALYs, in the Chinese population to provide more comprehensive information and explicit guidance for the future policy development of management strategies. Second, this study for the first time revealed the trend of COPD burden over time, which fill the gap in the long-term trend of the COPD burden in China. Third, we firstly explored the significant association between COPD burden and socioeconomic development, that can supply a scientific basis for COPD controlling and health facilities planning. However, several limitations should be acknowledged which are subjected to all the limitations of the GBD studies. First, the GBD 2019 estimated the models of COPD mainly through the available data of previous literatures at the national and provincial levels. The absence of relevant data in some provinces might have led to bias in the model estimates. Second, although the quality of ICD coding in death certificates in China has improved during the study period, there were substantial differences between provinces. Particularly, long-term trends in low SDI provinces with high mortality, such as Tibet, may be influenced by the redistribution of garbage codes. Third, because most COPD patients were identified by spirometry, underdeveloped regions with a lack of spirometric evaluation might have a high rate of misdiagnosis and underdiagnosis. Fourth, although the uncertainty was propagated in each step of modelling strategy in the GBD studies, some uncertainties might have not been fully captured in some regions without sufficient data.