Preventing Chronic Disease: July 2010: 09_0250 / A Summary Measure of Health Inequalities for a Pay-for-Population Health Performance System

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A Summary Measure of Health Inequalities for a Pay-for-Population Health Performance System

Yukiko Asada, PhD
Suggested citation for this article: Asada Y. A summary measure of health inequalities for a pay-for-population health performance system. Prev Chronic Dis 2010;7(4). http://www.cdc.gov/pcd/issues/2010/jul/09_0250.htm. Accessed [date].

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Abstract
A system that rewards population health must be able to measure and track health inequalities. Health inequalities have most commonly been measured in a bivariate fashion, as a joint distribution of health and another attribute such as income, education, or race/ethnicity. I argue this practice gives insufficient information to reduce health inequalities and propose a summary measure of health inequalities, which gives information both on overall health inequality and bivariate health inequalities. I introduce 2 approaches to develop a summary measure of health inequalities. The bottom-up approach defines attributes of interest, measures bivariate health inequalities related to these attributes separately, and then combines these bivariate health inequalities into a summary index. The top-down approach measures overall health inequality and then breaks it down into health inequalities related to different attributes. After describing the 2 approaches in terms of building-block measurement properties, aggregation, value, data and sample size requirements, and communication, I recommend that, when data are available, a summary measure should use the top-down approach. In addition, a strong communication strategy is necessary to allow users of the summary measure to understand how it was calculated and what it means.


Introduction
Developers of any performance reward system must select the performance improvements that deserve rewards and ensure fairness by measuring them appropriately. Measurement is arguably more challenging in pay-for-performance systems that reward population health than those that reward medical care because determinants of population health go beyond medical care. The questions sketched by Kindig (1) summarize challenges of measurement in a pay-for-performance system that rewards population health: 1) How should we measure health outcomes?, 2) How should we measure health inequalities?, and 3) How should we balance the need for improvement in both?

This article focuses on the second question and calls for development of a summary measure of health inequalities, where health inequalities associated with multiple attributes (such as income, education, and race/ethnicity) are summarized into 1 number. I assume typical measures of population health, such as life years or health-adjusted life years, and population units that have a mandate for the health of their population, such as states. However, the core idea of a summary measure presented here can in principle be applied to other measures of population health and other population units.

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Preventing Chronic Disease: July 2010: 09_0250