Chronic Respiratory Diseases: A Global View

Chronic respiratory diseases (CRDs) are among the most common non-communicable diseases worldwide, largely due to the ubiquity of noxious environmental, occupational and behavioral inhalational exposures (1). In addition to chronic obstructive pulmonary disease (COPD) and asthma, CRDs include interstitial lung diseases, pulmonary sarcoidosis, and pneumoconioses such as silicosis and asbestosis. Unfortunately, CRDs have received proportionately less public attention and less research funding compared to other disease entities such as cardiovascular disease, cancer, stroke, diabetes mellitus and Alzheimer’s disease (2, 3). Therefore, to better inform prevention, screening, treatment and research efforts dedicated to CRDs, it is key to understand their prevalence, morbidity and mortality, both on global and regional scales.

In The Lancet Respiratory Medicine, Joan Soriano and colleagues leverage the Global Burden of Diseases, Injuries and Risk Factors Study (GBD) to estimate the prevalence and attributable health burden of CRDs (4). They found that close to 545 million people in the world had a CRD in 2017, an increase of 39.8% since 1990. The High-Income region had the highest prevalence of CRDs, while the regions of South Asia and Sub-Saharan Africa had somewhat surprisingly the lowest prevalence. The most common CRDs were COPD and asthma with a worldwide prevalence of 4.1% and 3.7%, respectively. CRDs accounted for 3.9 million deaths in 2017, up 17.8% from 1990. They were also responsible for 1,470 disability-adjusted life years (DALYs) per 100,000 individuals in 2017, up 13.3% from 1990. South Asia had the highest CRD-attributable mortality rate, while Sub-Saharan Africa had the lowest. COPD and asthma were the top causes of CRD-related deaths worldwide, but interstitial lung diseases and pulmonary sarcoidosis were the second leading cause of death in the High-Income, Latin America and Caribbean, and Central Europe/Eastern Europe/Central Asia regions. While the absolute estimates of prevalence and health burden of CRDs increased between 1990 and 2017, the age-standardized estimates of prevalence, mortality and DALYs in the same time period actually decreased by 14.3%, 42.6% and 38.2%, respectively. Smoking accounted for the highest proportion of CRD-attributable disability in all regions for men. However, for women, the leading risk factor of CRD-attributable disability varied by region; it was household air pollution from solid fuel use in South Asia and Sub-Saharan Africa, exposure to ambient particulate matter in Southeast Asia/East Asia/Oceania and the Middle East and North Africa region, and smoking in all other regions.

Not only do these findings confirm that CRDs are common and associated with substantial morbidity and mortality, but they also highlight the heterogeneity of CRD-related health burden and risk factors by world region and sex. However, some of these estimates should be interpreted with caution. For example, the lower prevalence of CRDs in South Asia and Sub-Saharan Africa may be due to underdiagnosis in the setting of lack or underutilization of diagnostic capabilities (5). Further, lower CRD mortality rates in Sub-Saharan Africa may reflect differences in the age distribution of the population towards younger individuals where deaths from communicable diseases occur in greater frequency than deaths from chronic diseases (6). In addition, imperfect clinical case definitions likely affect the accuracy of some of the reported figures. For instance, a non-insignificant number of individuals between the ages of 5 and 24 years are reported as having COPD, which would be unexpected.

Despite these limitations, this study provides an important framework to spur much needed action to address the growing burden of CRDs worldwide. First, ramping up global, regional and local tobacco and pollution control measures is paramount. A separate GBD report had showed that levels of ambient particulate matter pollution, ambient ozone pollution and several occupational exposures have increased significantly between 1990 and 2017 (7). In addition, many countries are still facing rising smoking epidemics, especially among women and adolescents (8). Second, efforts should be deployed to promote early diagnosis and treatment of CRDs with the goal of improving long-term clinical outcomes, including premature mortality. A significant number of individuals living with a CRD remain unfortunately undiagnosed, even in developed countries (9). Timely detection of CRDs requires adequate access to and utilization of diagnostic instruments such as spirometry and chest imaging, but also effective and practical case-finding approaches (10). Third, increasing research funding is essential to develop strategies to detect CRDs at their earliest stage and also help accelerate the discovery of novel therapies which are currently sorely needed for many of these diseases. As an example of funding disparity, cannabis-related research received $220 million dollars in U.S. National Institutes of Health funding in 2019, compared to $112 million dollars for COPD research (11).

The age-standardized declines in the prevalence, morbidity and mortality of CRDs over the last three decades are encouraging. These trends should inspire governments, world organizations, medical societies, health systems, healthcare providers and individuals in the community to continue to advocate for clean air, tobacco-free environments and access to care. Similar to the concept of cardiovascular health, it is time to shift the paradigm from prevention of respiratory disease to the promotion of respiratory health (12). Such an initiative calls for continued research on individual- and population-level factors associated with increased susceptibility to impaired respiratory health.