Disability-adjusted life years (cont.)

The following figure portrays the 18 components of the most recent GBD study. They all contribute to the production of estimates of the YLL, YLD and DALYs attributable to different diseases and injuries (Box 13) and to selected risk factors (Box 18).

Source: Institute for Health Metrics and Evaluation (2013).

Estimates of all-cause mortality (Box 2) and mortality by cause (Boxes 3-5) are required to calculate YLL. Estimates of the prevalence of the impairments that result from each disease (Boxes 6-9, 11) and assumptions about their severity (Box 10) are required to calculate YLD. By aggregating the YLD by cause for each age and combining the results with the estimates of all-cause mortality, one can produce estimates of healthy life expectancy (Box 12). The risk factor analysis involves a separate exercise to redistribute the DALYs attributed to different diseases to the risk factors for them (Boxes 14-17). Lastly, no information on mortality by cause or on risk factor exposure is available for some countries and these measures have to be estimated using a regression model fitted to countries for which data exist. Making these estimates requires the covariate database (Box 1).

These different sets of components of a GBD study are discussed in more detail in subsequent sections of this session.