Performance Assessment of a Heat Wave Vulnerability Index for Greater London, United Kingdom

This study reports on the assessment of a multivariate heat wave vulnerability index (HVI) developed for London, United Kingdom. The HVI is assessed in terms of its ability to predict whether mortality and ambulance callout attain above average levels during heat wave events. Three approaches to assessment were adopted: 1) calculation of categorical statistics and associated skill scores for the dichotomous situation that above average mortality or ambulance callout occurred or not, 2) the degree to which relative risk of the aforementioned health outcomes changed with an increase in heat vulnerability as established using Poisson regression analysis, and 3) an independent samples test of the difference of mean mortality and ambulance callout between census units with and without high heat exposure and high vulnerability. The assessment results reveal that the HVI and a simple single variable index that represents age as a heat risk factor (the elderly index) offer potential as a priori indicators of the level of ambulance callout and mortality for all summer days and heat wave events, respectively. Based on the assessment results the utility of the HVI for heat risk management is discussed.