Disability weights

Every impairment has to be assigned a disability weight varying between 0 and 1 in order to make it comparable with other sequelae of disease and the YLL resulting from premature death from each disease.

For the initial iterations of the 1990 GBD study, the sequelae of disease were assigned to six classes of disability according to how severely they limited individuals’ ability to perform normal and instrumental activities of everyday living. Each disability class was then assigned a weight based on the views of a panel of health care professionals. The weights ranged from 0.096 for impairments that limited a person’s ability to perform at least one recreational, educational, procreational or occupational activity to 0.920 for impairments that left the individual in need of assistance to perform basic personal care activities such as eating, washing or using the toilet.

For the final 1990 GBD estimates and subsequent GBD studies prior to 2010, this procedure was revised. First, the weights for each class of disability were re-estimated based on an assessment of the degree of disability resulting from 22 indicator impairments rather than a generalised description of the degree of disability involved. Then disability caused by each form of impairment was distributed across the six classes of disability. Lastly, the final disability weight for that impairment was calculated as its average value across the six classes weighting by this distribution.