Asthma and COPD: Updates on Prevalence, Disability, and Mortality

A new study published in The Lancet Respiratory Medicine reports estimates of prevalence, death, and disability associated with asthma and chronic obstructive pulmonary disease (COPD).¹

Asthma and COPD, the most common chronic respiratory diseases, are among the top 20 causes of global disability. In addition, they have been identified as the 23rd and 8th causes, respectively, of disease burden as indicated by disability-adjusted life years (DALYs).^2,3 “Yet the measurement of mortality, prevalence, and other population indicators of these 2 diseases is complicated by misclassification and an absence of consensus about case definitions,” the researchers wrote. For example, asthma is often misclassified as COPD in elderly patients, and the 2 diseases may in fact overlap.^4,5

The present analysis estimated the prevalence, mortality, and disease burden of asthma and COPD from the Global Burden of Disease (GBD) Study 2015. The researchers used the GBD Cause of Death Ensemble modeling (CODEm) tool to estimate death rates due to each disease, and a variety of other methods to estimate disease prevalance and other factors. 

Between the 1990 GBD report and the 2015 GBD report, the following trends have emerged:

• The global death rate for COPD increased by 11.6% (95% uncertainty interval [UI], 5.3% to 19.8%), to 3.2 million (95% UI, 3.1 to 3.3 million). Although the age-standardized death rate for COPD decreased by 41.9% (95% UI, 37.7% to 45.1%), the reduction was counteracted by growth and aging of the global population.
• COPD prevalence increased by 44.2% (95% UI, 41.7% to 46.6%), while the age-standardized prevalence decreased by 14.7% (95% UI, 13.5% to 15·9%).
• The global death rate for asthma decreased by 26.7% (95% UI (–7.2% to 43.7%), to 0.40 million (95% UI, 0.36 to 0.44 million), and the age-standardized death rate for asthma decreased by 58.8% (95% UI, 39% to 69%).
• Asthma prevalence increased by 12.6% (95% UI, 9.0% to 16.4%), while the age-standardized prevalence decreased by 17.7% (95% UI, 15.1% to 19.9%).
• There was an increase in age-standardized DALY rates due to COPD until the middle range of the sociodemographic index (SDI; a composite measure of per capita income, mean years of education over age 15, and total fertility rate) before declining sharply. These rates varied for years lived with disability and years of life lost (YLLs) across the SDI continuum. 
• Age-standardized DALY rates due to asthma decreased monotonically with increasing SDI, and this association was attributed to variation in YLLs.

The findings further revealed that the main COPD risk factors were smoking and ambient particulate matter. These and additional risk factors including household air pollution, ozone, secondhand smoke, and occupational particulates explained 73.3% (95% UI, 65.8% to 80.1%) of DALYs due to COPD. The only risk factors quantified for asthma in GBD — smoking and occupational asthma — explained 16.5% (95% UI, 14.6% to 18.7%) of DALYs due to asthma.

Although much of the burden associated with asthma and COPD “is either preventable or treatable with affordable interventions, these diseases have received less attention than other noncommunicable diseases,” the researchers noted. “Up-to-date population information on these diseases is key to policy-making to improve access to and quality of existing intervention strategies.”

References

1. GBD 2015 Chronic Respiratory Disease Collaborators. Global, regional, and national deaths, prevalence, disability-adjusted life years, and years lived with disability for chronic obstructive pulmonary disease and asthma, 1990-2015: a systematic analysis for the Global Burden of Disease Study 2015 [published online August 16, 2017. Lancet Respir Med. 2017. doi:10.1016/S2213-2600(17)30293-X
2. GBD 2015 Mortality and Causes of Death Collaborators. Global, regional, and national life expectancy, all-cause mortality, and cause-specific mortality for 249 causes of death, 1980–2015: a systematic analysis for the Global Burden of Disease Study 2015. Lancet. 2016;388(10053):1459-1544. doi:10.1016/S0140-6736(16)31012-1
3. GBD 2015 Disease and Injury Incidence and Prevalence Collaborators. Global, regional, and national incidence, prevalence, and years lived with disability for 310 diseases and injuries, 1990–2015: a systematic analysis for the Global Burden of Disease Study 2015. Lancet. 2016;388(10053):1545-1602. doi:10.1016/S0140-6736(16)31678-6
4. Burney P, Jarvis D, Perez-Padilla R. The global burden of chronic respiratory disease in adults. Int J Tuberc Lung Dis. 2015;19(1):10-20. doi:10.5588/ijtld.14.0446
5. Yáñez A, Cho S-H, Soriano JB, et al. Asthma in the elderly: what we know and what we have yet to know. World Allergy Organ J. 2014;7(1):8. doi:10.1186/1939-4551-7-8