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 2000-2015, with the WHO African region having attained the largest decline (340%). This region, however, still bore the highest burden in 2015, 637 DALYs per 1000 population. This is over two-fold the burden of disease in the region with the lowest DALY rates (273 per 1000 population) in 2015: the WHO Western Pacific region. However the WHO Western Pacific region also experienced the lowest decline (6%) in DALY rate per 1000 population: from 513 in 2000 to 373 per 2015.
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 64% in the WHO Region of the Americas to 85% in the WHO African region in 2015. All regions have seen modest reduction (6-9%) in the contribution of premature death between 2000 and 2015.
Globally, 31% of total DALYs were caused by communicable, maternal, neonatal and nutritional causes in 2015, a decline from 44% in 2000. The WHO African region has strikingly high proportion (62%) of DALYs due to communicable, maternal, neonatal and nutritional causes compared to other regions.. In the WHO European Region and WHO Western Pacific Region, at least 80% DALYs were due to noncommunicable diseases. Road injuries caused a loss of nearly 76 million years of full health among the world’s population in 2015; making it among the 10 leading causes of DALYs.
The proportion of total DALYs borne by children under 15 years old globally declined from 41% in 2000 to 28% in 2015, 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 42% of total DALYs in 2015 (up from 37% in 2000), and people aged 60 years and older bore the remaining 30% (up from 22% in 2000).