A systematic literature review of disability weights measurement studies: evolution of methodological choices

Abstract

Background: The disability weight is an essential factor to estimate the healthy time that is lost due to living with a certain state of illness. A 2014 review showed a considerable variation in methods used to derive disability weights. Since then, several sets of disability weights have been developed. This systematic review aimed to provide an updated and comparative overview of the methodological design choices and surveying techniques that have been used in disability weights measurement studies and how they evolved over time.

Methods: A literature search was conducted in multiple international databases (early-1990 to mid-2021). Records were screened according to pre-defined eligibility criteria. The quality of the included disability weights measurement studies was assessed using the Checklist for Reporting Valuation Studies (CREATE) instrument. Studies were collated by characteristics and methodological design approaches. Data extraction was performed by one reviewer and discussed with a second.

Results: Forty-six unique disability weights measurement studies met our eligibility criteria. More than half (n = 27; 59%) of the identified studies assessed disability weights for multiple ill-health outcomes. Thirty studies (65%) described the health states using disease-specific descriptions or a combination of a disease-specific descriptions and generic-preference instruments. The percentage of studies obtaining health preferences from a population-based panel increased from 14% (2004-2011) to 32% (2012-2021). None of the disability weight studies published in the past 10 years used the annual profile approach. Most studies performed panel-meetings to obtain disability weights data.

Conclusions: Our review reveals that a methodological uniformity between national and GBD disability weights studies increased, especially from 2010 onwards. Over years, more studies used disease-specific health state descriptions in line with those of the GBD study, panel from general populations, and data from web-based surveys and/or household surveys. There is, however, a wide variation in valuation techniques that were used to derive disability weights at national-level and that persisted over time.

Keywords: Burden of disease; Disability adjusted life years; Disability weight; Valuation of health states.

Fig. 1

Flow diagram of existing disability weights measurement studies

Fig. 2

Number of disability weights measurement studies per country A map illustrating the number of studies that estimated disability weights for multiple heath states of disease. Countries in grey indicate that no studies met our eligibility criteria or they have not yet estimated disability weights.

Fig. 3

Number of disability weights measurement studies published between 1996 and 2021

Fig. 4

Evolution of methodological design choices in disability weights measurement studies: (A) Description of health states, (B) Panel of judges, (C) Valuation methods for health states, (D) Time Presentation, and (E) Surveying technique