Assessments and developments in constructing a National Health Index for policy making, in the United Kingdom

Composite indicators are a useful tool to summarize, measure and compare changes among different communities. The UK Office for National Statistics has created an annual England Health Index (starting from 2015) comprised of three main health domains - lives, places and people - to monitor health measures, over time and across different geographical areas (149 Upper Tier Level Authorities, 9 regions and an overall national index) and to evaluate the health of the nation. The composite indicator is defined as a weighted average (linear combination) of indicators within subdomains, subdomains within domains, and domains within the overall index. The Health Index was designed to be comparable over time, geographically harmonized and to serve as a tool for policy implementation and assessment. We evaluated the steps taken in the construction, reviewing the conceptual coherence and statistical requirements on Health Index data for 2015-2018. To assess these, we have focused on three main steps: correlation analysis at different index levels; comparison of the implemented weights derived from factor analysis with two alternative weights from principal components analysis and optimized system weights; a sensitivity and uncertainty analysis to assess to what extent rankings depend on the selected set of methodological choices. Based on the results, we have highlighted features that have improved statistical requirements of the forthcoming UK Health Index.