Disability-adjusted life years (DALYs)
Mortality does not give a complete picture of the burden of disease borne by individuals in different populations. DALY is the summary measure used to give an indication of overall burden of disease. One DALY represents the loss of the equivalent of one year of full health. Using DALYs, the burden of diseases that cause premature death but little disability (such as drowning or measles) can be compared to that of diseases that do not cause death but do cause disability (such as cataract causing blindness).
The burden of disease, expressed in DALYs per 1000 population, has decreased in all regions during the period of 2000-2012, with the WHO African region having attained the largest decline (32%). This region, however, still bore the highest burden in 2012, 740 DALYs per 1000 population. This is almost three-fold the burden of disease in the region with the lowest DALY rates (273 per 1000 population) in 2012: the low- and middle-income countries in the WHO Western Pacific region. High-income countries experienced the lowest decline (7%) in DALY rate per 1000 population: from 323 in 2000 to 301 per 2012.
The contribution of premature death (measured by years of life lost or YLL), to overall burden of disease (measured by total DALYs) varied across region, ranging from 62% in high-income countries to 85% in the WHO African region in 2012. All regions have seen modest reduction in the contribution of premature death between 2000 and 2012.
Globally, one third of total DALYs were caused by communicable, maternal, neonatal and nutritional causes (referred to as “MDG conditions”) in 2012, a decline from 43% in 2000. The WHO African region has strikingly high proportion (65%) of DALYs due to the MDG conditions compared to other regions, with 10% due to HIV/AIDS alone. In high-income countries, 83% DALYs were due to noncommunicable diseases, including cardiovascular diseases (21%), cancers (17%) and mental disorders (12%). Road injuries caused a loss of nearly 80 million years of full health among the world’s population in 2012; making it among the 10 leading causes of DALYs.
The proportion of total DALYs borne by children under 15 years old globally declined from 40% in 2000 to 30% in 2012, reflecting the massive reduction in deaths among children under 5 years old during this period. Almost all (87%) of DALYs borne by children under 15 years old, however, were caused by premature death, the remaining 13% were caused by ill health and disability. Adults aged 15-59 years old bore 43% of total DALYs in 2012 (up from 38% in 2000), and people aged 60 years and older bore the remaining 27% (up from 22% in 2000).