Introduction In 1993 the World Bank sponsored a study to assess the global burden of disease in collaboration with the World Health Organization (WHO) and the Harvard School of Public Health (1-3). As well as generating comprehensive and consistent set of estimates of mortality and morbidity by age, sex and region for the world for the first time (4-6), the Global Burden of Disease (GBD) study also introduced a new metric – the disability adjusted life year (DALY) – to quantify the burden of disease. The DALY is a summary measure of population health that combines in a single indicator years of life lost from premature death and years of life lived with disabilities. One DALY can be thought of as one lost year of ‘healthy’ life and the burden of disease as a measurement of the gap between current health status and an ideal situation where everyone lives into old age free of disease and disability.