Background
As major public health issues worldwide, chronic respiratory diseases (CRDs), including chronic obstructive pulmonary disease (COPD), pneumoconiosis, asthma, interstitial lung disease and pulmonary sarcoidosis, impose appreciable socioeconomic burdens on individuals and societies. Compared with other noncommunicable diseases, such as cardiovascular disease, cancer, and diabetes, CRDs are seriously neglected [
1].
The most important risk factors for CRDs have been identified and include tobacco use, exposure to indoor and outdoor pollutants, allergens, occupational exposure, unhealthy diet, obesity, physical inactivity and other factors [
2]. Because of an accelerated aging population and increased exposure to risk factors, CRDs are becoming more prominent problems for all regions of the world. The epidemiology and disease burdens of CRDs vary substantially worldwide. Previous studies have estimated the prevalence of CRDs at the regional or national level but not at the global level [
3‐
5]. Understanding the prevalence and incidence trends of CRDs is vital for improving the control and prevention of CRDs.
The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2017 provided a comprehensive assessment of burden of CRDs in 195 countries and territories [
6]. Based on this important data source, we assessed the spatial and temporal trends in the prevalence and incidence of CRDs by age and sex from 1990 to 2017. It was estimated that the burden of chronic diseases, including CRDs, accounted for 80% of the total burden in developing countries [
7]. A negative association of socioeconomic status with the prevalence in COPD was revealed [
8]. Asthma prevalence was found to be highest in high-income regions [
9]. Therefore, the correlations between the incidence and the World Bank income levels, sociodemographic index (SDI), and human development index (HDI) levels were analyzed to assess the factors that affect incidence, and that is an important extension of previous research.
Discussion
In 2017, CRDs were still the leading causes of morbidity across the world. A large proportion of the disease burden was attributed to asthma and COPD. From 1990 to 2017, the new and total cases of CRDs increased globally, whereas the ASIRs and ASPRs experienced decreasing trends, which may be explained by the population growth.
COPD was the most prevalent CRD worldwide in 2017, accounting for 54.9% of CRDs. The incidence rate of COPD increased with age in both sexes and decreased in all age groups from 1990 to 2017, except for elderly patients older than 80 years. At the national level, Japan ranked among the top three countries with the lowest ASIRs, whereas Papua New Guinea and North Korea had the highest ASIRs in 2017. Large inequities in COPD burden existed in different SDI regions. A significant decrease in the ASIR was observed in the high-middle-SDI regions. The bulk of the burden of COPD still occurred in the low-SDI regions.
Pneumoconiosis is mainly attributed to occupational risk factors, and a minimum proportion of cases may be caused by the natural environment or second-hand exposures [
13]. Significant differences in incidence stratified by sex were observed for pneumoconiosis, which emerged as a male-predominant condition in people older than age 20. The sex-specific incidence of pneumoconiosis has a correlation with sex-specific occupational exposure. The temporal decline in the ASIR of pneumoconiosis was partly due to less occupational exposure. However, the ASIR for asbestosis showed an increasing trend, which might be partly explained by the long latency period between asbestos exposure and the manifestation of the disease [
14]. Pneumoconiosis remains an important occupational health problem in developing countries. In 2017, the highest ASIRs were noted in China, Papua New Guinea and North Korea. The countries classified as middle-SDI and upper-middle income had the highest ASIRs and experienced significant decreases in the ASIRs from 1990 to 2017.
Asthma is a serious global health problem that affects all age groups, especially children, as shown in Fig.
3. From 1990 to 2017, the global ASIR showed a decreasing tendency that turned into a slight increase. In our study, the global ASIR of asthma decreased with age. According to the data from Human Development Reports, there was a significant decline in the global population aged younger than 5 from 1990 to 2000. The number of people aged older than 15 increased during 1990–2017. The young age (0–14) dependency ratio (per 100 people ages 15–64) showed a decreasing trend. On the other hand, the urban population of the world who have higher rates of asthma than people in rural areas, have grown rapidly from 1990 to 2017. Therefore, the U-shaped temporal ASIR trend for asthma might be a result of fertility decline, population aging and urbanization. There was an inverse correlation between the ASIR and the SDI/HDI in 2017. Furthermore, the EAPC in ASIR was negatively related to the change of the SDI between 1990 and 2017, indicating that the incidence of asthma could be partly attributed to social and economic factors.
Interstitial lung diseases are a group of diffuse parenchymal lung disorders [
15] that are related to occupational or ambient air pollution exposures [
16]. Pulmonary sarcoidosis is an inflammatory lung disorder associated with ethnicity and latitude [
17]. Notably, there was an increasing trend in the global ASIR of interstitial lung diseases and pulmonary sarcoidosis from 1990 to 2017. The incidence in both sexes presented a steep rise after age 60 in both 1990 and 2017, and interstitial lung diseases and pulmonary sarcoidosis were much more prevalent in males than in females, suggesting that older males are particularly vulnerable. Although pulmonary sarcoidosis and lymphangioleiomyomatosis have a female predilection, [
17] occupational exposure as a major cause of interstitial lung disease was more common in males than in females.
An age distribution analysis revealed that the incidence of CRDs, except for asthma, increased with age and exhibited a strong increase in elderly people aged over 90 years. According to the World Health Organization, 2 billion people worldwide are expected to be 60 years or older by 2050, accounting for 22% of the world’s population. Therefore, aging populations will become a profound challenge for CRD control and prevention.
Tobacco use is an important risk factor for CRDs. It was estimated that the prevalence of tobacco use would decline by 25% for males and 42% for females from 1980 to 2020, which may contribute to the decrease in the incidence of CRDs [
18]. Sex and socioeconomic disparities in tobacco use have been identified. The cigarette smoking prevalence in males was more than four times higher than that in females worldwide [
19]. Globally, most of the countries with the lowest prevalence of tobacco use were low-income and middle-income countries, and the highest prevalence in both males and females was concentrated in Europe and the western Pacific [
20]. However, a sex or socioeconomic status disparity was not noted for the prevalence of CRDs or COPD; this result might be explained by other risk factors, including indoor air pollution, ambient air pollutant exposure, occupational particulate exposure.
A recent study revealed that the spatial heterogeneity of global particulate matter pollution significantly increased from 1998 to 2016. The most polluted areas were concentrated in developing middle-income regions, such as northern India, the central Indo-China Peninsula and southern and eastern China, which account for approximately 13.4% of the global land area and include 56% of the world’s population [
21]. The CRDs cases exposed to risk factors such as tobacco use and air pollution were not available in the GBD 2017 dataset, which limited the assessment of the influence of environmental pollution on the prevalence of CRDs in this study.
The relationships between the incidences and the SDI/HDI were assessed. Notably, the prevalence of missed diagnoses of CRDs varied across all five SDI regions and countries with different HDIs, [
22‐
25] thus affecting the estimated incidences of reported CRDs. In addition, the national epidemiologic survey on CRDs in many countries with large populations were not conducted in recent years, which may lead to an underestimation of the disease burden. Therefore, the results of this study could not accurately reflect the actual correlation between the incidences and the SDI/HDI in the real world.
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