Posted on | March 20, 2013 | 2 Comments
I was recently conversing with a group of public health students on the state of affairs throughout the world when the conversation wandered into the area of “Global Burden of Disease”. To my surprise, the level of knowledge and understanding of the term – its origins, purpose and intent – was highly variable. So here’s a refresher.
When was the Global Burden of Disease report first published?
The Global Burden of Disease study was published in Science in 1996.(1)
What did it examine?
It looked at the effect of disease not only on “lifespan” but also on “health span” for the first time. Investigators did so by moving beyond mortality rates and creating a new measure called DALY.(2)
What is a DALY?
DALY stands for disability adjusted life year and is a measure that expresses one year of life lost (YLL) to premature death plus years lived with a disability(YLD) of specified severity and duration; basically one year of life lost to poor health.
What is the difference between “lifespan” and “healthspan”?
Lifespan equals the number of years living, while health span equals the number of years of healthy living. These are two enormously different measures. We increasingly appreciate that disease and disability can significantly limit an individual’s productivity and happiness and radically alter individual, family and community well being.
Who led the study?
The study, extending over multiple years, was led by epidemiologist Alan Lopez of the WHO and Harvard professor Christopher Murray. They created a methodology to tract the combined pain, suffering, loss of productivity and unrealized hopes and dreams of Earth’s total human population.
Who was involved in the study?
The Global Burden of Disease study, begun in 1992, involved 100 collaborators in more than 20 countries. It attempted to quantify disease and injury burden of over 100 conditions and make projections out 30 years for 500 consequences or results of these conditions. In the analysis, over 50,000 estimates were made.(1,2)
What is “dual burden of disease”?
Dual burden of disease refers to two different causative paths for disease and disability. One path is communicable disease, believed to be more prevalent in developing nations. A second path is chronic, debilitating non-communicable diseases felt in the past to be restricted largely to developed nations.
In the original study, what were the top ten conditions contributing to burden of disease?
The top ten disease entities, from high to low, by the percentage of total years of healthy living that our global population loses as a result of specific disease or disability were:
1)respiratory diseases, 2)diarrheal diseases, 3)perinatal illnesses, 4)depression, 5)ischemic heart disease, 6)cerebrovascular disease, 7)tuberculosis, 8)measles, 9)motor vehicle accidents, 10)congenital birth defects
Did the study project forward?
Yes. The study predicted that by 2020 heart disease worldwide would achieve top billing, followed by depression, auto accidents, cerebrovascular disease and chronic obstructive pulmonary disease or emphysema. It also predicted the death and disability from armed conflicts and warfare would rise and reach a ranking of #8, and that HIV related deaths would reach a ranking of #10. In summary the study estimated that by 2020, 73% of the world’s disease burden would be due to chronic disease, 17% from infectious communicable diseases, and 10% from trauma. Tobacco was predicted to be the single leading cause of death and disability, with growing numbers especially in the developing world.(1,2)
Have there been any follow-up studies?
Yes. The Global Burden of Disease 2010 Project was reported out in Lancet in December, 2012.(3) It tracked 67 risk factors and 291 disease entities in 21 countries between 1990 and 2010. The study was funded by the Bill and Melinda Gates Foundation.
What were the findings?
Led by Harvard’s Christopher Murray, and involving some 375 investigators, the summary of results is as follows:
“Global DALYs remained stable from 1990 (2·503 billion) to 2010 (2·490 billion). Crude DALYs per 1000 decreased by 23% (472 per 1000 to 361 per 1000). An important shift has occurred in DALY composition with the contribution of deaths and disability among children (younger than 5 years of age) declining from 41% of global DALYs in 1990 to 25% in 2010. YLLs typically account for about half of disease burden in more developed regions (high-income Asia Pacific, western Europe, high-income North America, and Australasia), rising to over 80% of DALYs in sub-Saharan Africa. In 1990, 47% of DALYs worldwide were from communicable, maternal, neonatal, and nutritional disorders, 43% from non-communicable diseases, and 10% from injuries. By 2010, this had shifted to 35%, 54%, and 11%, respectively. Ischaemic heart disease was the leading cause of DALYs worldwide in 2010 (up from fourth rank in 1990, increasing by 29%), followed by lower respiratory infections (top rank in 1990; 44% decline in DALYs), stroke (fifth in 1990; 19% increase), diarrhoeal diseases (second in 1990; 51% decrease), and HIV/AIDS (33rd in 1990; 351% increase). Major depressive disorder increased from 15th to 11th rank (37% increase) and road injury from 12th to 10th rank (34% increase).”(3)
What were the study’s take-away observations?
1. Global disease burden has continued to shift away from communicable to non-communicable diseases and from premature death to years lived with disability.
2. This family of diseases is associated with metabolic inflammation, that is a low-grade chronic inflammatory state which adversely effects gene-environment interaction. A focus on basic science research and personalized health behavioral solutions will be required to modulate this burden as world populations age.
3. In sub-Saharan Africa, however, many communicable, maternal, neonatal, and nutritional disorders remain the dominant causes of disease burden.
4. The rising burden from mental and behavioral disorders, musculoskeletal disorders, and diabetes will impose new challenges on health systems.
5. Regional heterogeneity highlights the importance of understanding local burden of disease and setting goals and targets for the post-2015 agenda taking such patterns into account.(3)
For Health Commentary, I’m Mike Magee
1.Murray CJL, Lopez AD. Evidence based health policy lessons from Global Burden of Disease study. 1996. 274: 740-743.http://www.who.int/healthinfo/nationalburdenofdiseasemanual.pdf
2. Murray CJL, Lopez AD. Evidence based health policy. Science 1 November 1996: Vol. 274 no. 5288 pp. 740-743 DOI: 10.1126/science.274.5288.740 http://www.sciencemag.org/content/274/5288/740
3. Murray CJL et al. Disability-adjusted life years (DALYs) for 291 diseases and injuries in 21 regions, 1990—2010: a systematic analysis for the Global Burden of Disease Study 2010.http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(12)61689-4/abstract