 In 2004, the World Health Organization calculated that 1.5 billion disability-adjusted life years were lost to disease and injury.The first study on the global burden of disease, conducted in 1990, quantified the health effects of more than 100 diseases and injuries for eight regions of the world, giving estimates of morbidity and mortality by age, sex, and region.It also introduced the DALY as a new metric to quantify the burden of diseases, injuries, and risk factors.