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Common values in assessing health outcomes from disease and injury: disability weights measurement study for the Global Burden of Disease Study 2010

Published December 13, 2012, in The Lancet

Abstract

Measurement of the global burden of disease using disability‐adjusted life years (DALYs) requires disability weights that measure health losses for all non‐fatal consequences of disease and injury. There has been vigorous debate over the definition and measurement of these weights. The primary objective was a comprehensive re‐estimation of disability weights through a large‐scale, population‐based, empirical investigation in which judgments about health loss associated with many causes were elicited from the general public in diverse communities. This is a marked improvement over previous efforts, which relied solely upon judgments from a small group of health professionals.

Analytical approach

A major strength of this study is that it gathered data through household surveys and a web survey rather than from expert panels. The reliance on health professionals has been a frequent target criticism of previous studies. These weights should reflect a broad social understanding of the relative significance of different aspects of health.
 
The authors captured responses from both household surveys and web‐based surveys. 13,902 participants answered in‐person surveys in Bangladesh, Indonesia, Peru, Tanzania, and the United States (by telephone in the US, face-to-face elsewhere). An additional 16,328 participants from around the world completed a web survey. The web survey included respondents from most countries. Surveys were conducted through personal interviews in Bangladesh, Indonesia, Peru, and Tanzania; telephone interviews in the United States; and an open‐access web-based survey. The sites for the household surveys were selected to provide diversity in language, culture, and socioeconomic status, and the web-based survey included respondents from most countries of the world.
 
The surveys used paired‐comparison questions, in which respondents considered two hypothetical individuals with different functional limitations, and indicated which person they regarded as healthier. The web survey added population health equivalence questions, which compared the overall health benefits of different life saving or disease prevention programs.

Research findings

This study finds compelling evidence that contradicts the prevailing wisdom that disability weights must vary widely across samples with diverse cultural, educational, environmental, or demographic circumstances. The findings show there is a nearly universal construct of human health.
 
Respondents gave the highest disability weights to schizophrenia and severe multiple sclerosis, saying they had more than 10 times the impact on people’s lives than other conditions. Those surveyed assigned less weight to hearing loss, vision loss, infertility and even the loss of some limbs, but they gave more weight to drug use, epilepsy, and alcohol use.
 
Analysis of paired comparison responses indicated a high degree of consistency across the household, telephone, and web surveys. Correlations between individual survey results and results from analyses of the pooled dataset were also very high.
 
Education levels also seemed to have little effect on survey results. Comparing the web survey, which had the most highly educated respondents (more than 92% had higher than secondary schooling), to the survey in Tanzania, which had the respondents with the lowest average educational levels (1% had higher than secondary schooling), we found a correlation of 0.89 between these two surveys.

Policy implications

The study establishes a new set of disability weights that will be a critical resource for assessing disease burden and analyzing the effectiveness and cost of interventions. These new weights offer a more rigorous and credible basis for weighing outcomes than the previously measured weights.
 
Even as the world has changed dramatically over the past 20 years, how we view the impact of health conditions has remained relatively constant. There is also a broadly shared set of common values for health losses that transcends narrow cultural and geographic boundaries. The findings of this study suggest that concerns about variations in health assessments across settings may be overstated. GBD 2010 also reveals that people perceive many mild health conditions to have even less impact than previously thought.
 
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Citation

Salomon JA, Vos T, Hogan DR, Gagnon M, et al. Common values in assessing health outcomes from disease and injury: disability weights measurement study for the Global Burden of Disease Study 2010. The Lancet. 2012 Dec 13; 380: 2129–2143.

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