Global Burden of Disease Project

The Global Burden of Disease Project (GBDP) draws on a wide range of data sources to produce consistent estimates of the cost of morbidity and mortality worldwide, as defined by the years of healthy life lost due to injury and illness. The GBDP is conducted by the World Health Organization (WHO) and updates the Global Burden of Disease Study for the year 1990, whichwascommissionedbytheWorldBankandcarried out by the WHO and Harvard University in 1992. Both the original study and the GBDP quantify the burden of disease using the concept of the disabilityadjusted life year (DALY), which allows an estimation of the total years of healthy life in a population by combining two types of information. Years of life lost (YLL) represent the cost of premature mortality, calculated as the projected years a person was expected to live; years lost due to disability (YLD) represent the years of healthy life lost due to diminished quality of life caused by illness or disability. One DALY is equivalent to the loss of 1 year of life in full health, so that the DALY cost would be equivalent for a person in perfect health dying 1 year prematurely, or a person living 2 years in a health state judged to be half as desirable as the state of full health.

The primary advantage of using a common metric such as the DALY is that it allows comparison of the costs of disparate medical conditions and the benefits that might be gained by different interventions. It is particularly important that the DALY approach assigns a value to the cost of ill health as well as to death, allowing that an estimation of the societal cost of conditions such as hearing loss are seldom fatal but may significantly reduce an individual's quality of life. This approach is commonly used today but was an innovative concept when included in the 1990 report. The DALY approach allows governments and other policymakers to evaluate the costs of disparate medical conditions, make informed judgments about where to target resources in order to produce the greatest improvement in health for a given investment of resources, and evaluate the comparative effectiveness of interventions targeted at different conditions. Many countries have adopted the global burden of diseases (GBD) approach to guide national priorities in health research as well.

For 2001, the GBD found that, as in 1990, the most important causes of disability in all regions of [Page 437]the world were neuropsychiatric illnesses, which accounted for more than 37% of YLD for adults above 15 years worldwide. The greatest amount of loss of healthy life due to premature mortality was caused by noncommunicable conditions, including cancers, diabetes, and heart disease: These conditions accounted for almost 50% of DALYs lost in lowand middle-income countries and more than 85% of the loss in high-income countries.