August 17, 2017
Although overall prevalence and death rates for asthma and chronic obstructive pulmonary disease (COPD) declined between 1990 and 2015, population growth and aging have driven up worldwide numbers for these lung conditions, according to estimates from the 2015 Global Burden of Disease (GBD) Study published online August 16 in the Lancet Respiratory Medicine.
The GBD collaborators call for data-informed policy making and strategic interventions to decrease the burden of these noncommunicable diseases and improve care. They note that reducing the global toll will require action beyond smoking cessation, including a reduction in air pollutants in the community, home, and workplace. These include cooking fuel smoke, asbestos, diesel fumes, arsenic, and benzene.
"COPD and asthma are important contributors to the burden of non-communicable disease," write Theo Vos, MD, PhD, professor of global health at the Institute for Health Metrics and Evaluation at the University of Washington, Seattle, and colleagues.
"Although much of the burden is either preventable or treatable with affordable interventions, these diseases have received less attention than other prominent non-communicable diseases like cardiovascular disease, cancer, or diabetes."
Dr Vos and associates also stress the need for the collection of up-to-date population-based information to improve access and quality of care. They caution that because of global variations in disease definitions and data quality, the study's estimates are somewhat uncertain, and hence the report includes uncertainty intervals (UIs) with its figures. The estimates are based on published papers, unpublished reports, surveys in the GBD's Global Health Data Exchange repository, and US healthcare services data.
Deaths caused by COPD rose by 11.6% (95% UI, 5.5% - 19.8%) during the 25-year study, going from 2.8 million in 1990 to 3.2 million (95% UI, 3.1 million - 3.3 million) in 2015. Cases increased by 44.2% (95% UI, 41.7% - 46.6%), going from 121 million to 174.5 million (95% UI, 160.2 million - 189.0 million).
In terms of prevalence, the greatest decrease in age-standardized COPD prevalence occurred in countries in the middle and high-middle quintiles of the sociodemographic development index, a measure calculated on lagged distributed income per capita, average years of education after age 15 years, and total fertility rate.
In 2015, COPD caused 2.6% of global disability-adjusted life years (DALYs), a measure of overall disease burden based on the number of years lost as a result of ill-health, disability, or early death. Asthma accounted for 1.1%.
During the study, asthma deaths declined by an estimated 26.2% from 0.55 million to 0.40 million, but asthma prevalence increased by 12.6%, going from 318.2 million to 358.2 million cases (95% UI, 323.1 million - 393.5 million).
The greatest disability burden imposed by both diseases was borne by developing countries.
Overall, the lowest COPD burden emerged in high-income countries in the Asia Pacific region such as Japan and Singapore, as well as central Europe, North Africa, the Middle East, the Caribbean, Western Europe, and Andean Latin America, with some countries having DALY rates below 300 per 100,000 population.
In contrast, the low-income countries of Papua New Guinea, India, Lesotho, and Nepal had the highest COPD burden, with age-standardized DALY rates for both sexes between 2001 and 4500 per 100,000 population.
The United States landed in the middle, with a DALY rate of 601 to 1000, whereas its neighbors to the north and south, as well as Scandinavia and the United Kingdom, all came in lower, at 301 to 600.
Meanwhile, DALY rates for asthma were comparable among the United States, Canada, and Mexico, at 201 to 300 per 100,000.
As for asthma, the toll was highest in Afghanistan, the Central African Republic, Fiji, Kiribati, Lesotho, Papua New Guinea, and Swaziland, where age-standardized DALY rates topped 1200 per 100,000 people. Countries in Eastern and Central Europe, such as Russia and the Balkans, as well as China, Italy, and Japan, experienced the lowest burden, with DALY rates of 100 to 200 per 100,000. The United Kingdom was moderately high, at 501 to 800.
As for risk factors, smoking and ambient particulate matter were identified as the main culprits in COPD, followed by household air pollution, workplace particulates, ozone, and secondhand smoke. These combined risks accounted for 73.3% of COPD-related DALYs. Fewer risks were quantified for asthma, with smoking and workplace triggers explaining 16.5% of asthma-related DALYs.
The collaborators called for more standardized data collection in terms of case definition and severity. "The varied definitions of asthma and COPD around the world mean many people are not diagnosed or are incorrectly diagnosed. For this reason, we need much clearer understanding of how the diseases develop to help us identify cases more conclusively," Dr Vos said in a news release.
"More, and updated, population measurements of COPD and asthma are needed to better quantify the size of the problem, to benchmark with other chronic conditions associated with smoking and ageing, and with any other environmental and air pollution," Dr Vos and colleagues write in their article.
Commenting on the GBD study in a related comment, Onno C.P. van Schayck, MD, PhD, and Esther A. Boudewijns, BSc, from Maastricht University, the Netherlands, stress that interventions must target modifiable risk factors over and above smoking. Although initiatives to reduce smoking worldwide have reduced COPD prevalence, they write, "Now is the time to tackle ambient and household air pollution, which together cause more DALYs than smoking alone." The commentators were not involved in the GBD report.
In developing countries, biomass fuels are among the greatest causes of air pollution. "Nowadays, more than half of the world's population uses biomass fuel as a primary cooking source, resulting in a high burden of morbidity and mortality," the commentators write.
Although cleaner fuels would cut household air pollution, there are financial and practical barriers to switching constraints, especially in urban slums. "It is estimated that 1.8 billion people will still be reliant on solid biomass for cooking in 2040," Dr van Schayck and Dr Boudewijns write. "Consequently, interventions should also aim to include the development of low-smoke biomass cooking stoves." Dr van Schayck has collaborated on the development of a cooking stove that removes smoke from the home.
The commentators support the GBD researchers' call for the international formulation of usable definitions for asthma and COPD.
This study was funded by the Bill & Melinda Gates Foundation and conducted by the Institute of Health Metrics and Evaluation, University of Washington, Seattle. The study collaborators and the commentators have disclosed no relevant financial relationships.