Global Burden of Disease

The Global Burden of Disease (GBD) database is a comprehensive and coherent analysis of mortality and disability due to ill health for all world regions ^[1]. The disability-adjusted life-year (DALY) is the health measure that is used to determine the overall burden of disease.

History and Aims of the GBD

The GBD database is derived from a study that began in 1992 by Christopher Murray of Harvard University’s School of Public Health, Alan Lopez and his colleagues at the World Health Organization (WHO), and the World Bank. Its primary aims were: (1) to stimulate dialogue regarding the inclusion of non-fatal health outcomes in international health policy debates; (2) to create an objective assessment of estimates of mortality or disability by separating out epidemiological assessment from advocacy; and (3) to develop a measure that quantified the burden of disease and could be applied in cost-effectiveness analyses ^[2]. The GBD database provides the most comprehensive and internally consistent estimates of mortality and morbidity by age, sex, and region ^{[3] [4]}.

Disability-Adjusted Life-Year

Prior to this landmark study, mortality-based indicators such as life expectancy, all-cause mortality, and disease-specific mortality were used to evaluate health in human populations for comparisons between localities, nations, and regions. However, these indicators did not account for the contributions of chronic disease, injury, or disability. As one researcher argues, previous measures “provided insufficient information to make any but the most basic judgments about the health of a population or the comparative impact of an intervention” ^[5]. To reconcile this gap of information, summary measures known as health-adjusted life-years (HALYs) were developed to assess the combined impact of both mortality and morbidity. HALYs include disability-adjusted life-years (DALYs) and quality-adjusted life-years (QALYs).

The DALY is the primary metric used by the GBD, and was developed for the following reasons: (1) to quantify the burden of diseases, injuries, and risk factors; (2) to set priorities for resource allocation during policymaking; and (3) to measure the gap between a population’s health and a hypothetical ideal for health achievement ^[5].. The DALY is a single measure calculated from years of life lost due to premature mortality (YLL) and years of life lived in less than full health (YLD) ^[4]. DALY estimates of more than 100 diseases and injuries for eight regions of the world were published in the first release of the GBD in 1990. Later releases of the GBD contain expanded lists of diseases, injuries, and risk factors, and the 2005 GBD report is currently being conducted ^[1].

Highest Disease Burdens

The GBD database categorizes diseases into three broad cause groups: (1) communicable, maternal, and perinatal conditions and nutritional deficiencies; (2) non-communicable diseases (e.g. cardiovascular diseases, cancers); and (3) injuries. According to the GBD database, the leading burdens of disease in high-income countries come from mostly category two diseases (e.g. cardiovascular disease), whereas low-income countries have a greater burden of category one diseases (e.g. perinatal conditions and lower respiratory infections) in addition to category two diseases ^[4]. The leading causes of mortality and burden of disease (in DALYs) in 2004 can be seen in Figure 1. Projections for the year 2030 can be seen in Figure 2. These figures can be found on the WHO’s GBD website ^[1].

Resource allocation using the GBD

Many national and international organizations, including the United States Institute of Medicine, have argued for allocation of funding based on the GBD database. They state that appropriation of resources should be based on the number of DALYs contributed by specific diseases. A recent study found an association between National Institutes of Health funding and the burden of disease, but notes that conclusions vary depending on the type of measure used (e.g., YLLs, YLDs, DALYs)^[6]. Some diseases such as AIDS and breast cancer were determined to receive more funding than predicted, whereas diseases such as COPD and perinatal conditions were found to receive less ^[7]. HIV/AIDS has been found to receive the most funding, which was in accordance with calculated burden using DALYs.

In contrast, other studies do not appear to show a linear relationship between disease burden and analyzed spending patterns. A separate study of donor funding priorities found that while acute respiratory infections account for a quarter of the burden due to communicable diseases, they receive less than 3% of aid ^[8].

It appears that the distribution of funding for the burden of disease may not correlate with level of disease burden. While it is reasonable to consider allocating resources based on current burden, some researchers argue that factors beyond the burden of disease also need to be considered in funding allocation, including the need to control and predict future burdens, funding contributed by the private sector/private interests, and scientific potential ^[6][7]. Though this debate continues, the GBD database remains a valuable, coherent, consistent, and comprehensive metric for evaluating the global burden of death and disability.

Figure 1: Leading causes of mortality and burden of disease in the world, GBD 2004 ^[1].

Figure 2: Ten leading causes of burden of disease, world, 2004 and 2030 ^[1].

References

1. ↑ ^{1.0 1.1 1.2 1.3 1.4} The World Health Organization. The Global Burden of Disease. <http://www.who.int/healthinfo/global_burden_disease/about/en/index.html> Accessed on 20 March 2010.
2. ↑ Murray CJL and Lopez AD. The Global Burden of Disease: A comprehensive assessment of mortality and disability from diseases, injuries, and risk factors in 1990 and projected to 2020. Harvard University Press. 1996.
3. ↑ Murray CJL, Lopez AD. Global health statistics. Cambridge: Harvard University Press, 1996.
4. ↑ ^{4.0 4.1 4.2} Lopez AD, Mathers CD, Ezzati M, Jamison DT, and Murray CJL. Global and regional burden of disease and risk factors, 2001: systematic analysis of population health data.
5. ↑ ^{5.0 5.1} Gold MR, Stevenson D, Fryback DG. HALYs and QALYs and DALYs, Oh My: Similarities and differences in summary measures of population health. Annu. Rev. Public Health 2002. 23:115-34.
6. ↑ ^{6.0 6.1} Gross CP, Anderson GF, Powe NR. The relation between funding by the National Institute of Health and the burden of disease. NEJM 1999. 340: (24)1881-1888.
7. ↑ ^{7.0 7.1} Rovner J. NIH allocates funding by burden of disease. Lancet. 1999. 353:2220.
8. ↑ Shiffman J. Donor funding priorities for communicable disease control in the developing world. Oxford University Press, 2006.