Academic journal article Environmental Health Perspectives

Multiple Trigger Points for Quantifying Heat-Health Impacts: New Evidence from a Hot Climate

Academic journal article Environmental Health Perspectives

Multiple Trigger Points for Quantifying Heat-Health Impacts: New Evidence from a Hot Climate

Article excerpt

Introduction

Many studies have retrospectively examined high environmental temperature and mortality. This research has largely focused on estimating excess deaths from all-cause mortality and on the statistical identification of a single threshold temperature above which deaths increase (e.g., Hajat and Kosatsky 2010; McMichael et al. 2008). Importantly, the temperature thresholds identified in such studies have been proposed as a basis for the activation of heat-health warning systems and other public health interventions (e.g., Henderson and Kosatsky 2012; Pascal et al. 2006). Other applications of retrospective analyses include assessment of the potential future health effects of local-, regional-, or global-scale climate change (e.g., Huang et al. 2011).

A related and rapidly accumulating body of research assesses the relationship between high temperature and health events other than mortality: hospital admissions and emergency department (ED) visits (Hess et al. 2014; reviews by Kravchenko et al. 2013; Martiello and Giacchi 2010; Ye et al. 2012), hospital admissions among patients seen in the ED (Pillai et al. 2014), ambulance/emergency response calls (Alessandrini et al. 2011; Hartz et al. 2013; Nitschke et al. 2011; Schaffer et al. 2012; Williams et al. 2012a, 2012b), teleradiology calls (Brunetti et al. 2014), and outpatient visits (Pudpong and Hajat 2011). However, only a few studies have considered more than one measure of health effects associated with heat, for a single geographic region, at the same time (e.g., Kovats et al. 2004; Williams et al. 2012a, 2012b).

The fact that extreme heat persists as a public health challenge (Berko et al. 2014) despite compelling evidence for its adverse effects on health calls for new approaches toward preparedness and intervention strategies. Here, we propose that it is possible to better understand and mitigate the current and future risks posed by high temperatures with adaptation strategies based on comprehensive and contextualized weather information spanning a range of health outcomes associated directly and indirectly with heat.

Opportunities for improving public health strategies aimed at mitigating the effects of heat on health may lie at the intersection of many of the ideas and methodologies that have been brought forward to date. For example, functional forms of heat-health relationships are dependent on the local setting (Anderson and Bell 2009; Curriero et al. 2002). In addition, the relationship between temperature and mortality and morbidity may have different functional forms within a given location (Kovats et al. 2004). Intervention strategies aimed at particular populations (e.g., outdoor workers vs. elderly residents) would be most effective if they considered the diagnosis and severity of health events that are most relevant for that population. Furthermore, various definitions of temperature thresholds are employed in the literature, some of which are brought forward with little more than generalities about the purpose of identifying such metrics. The suite of different conceptualizations of "thresholds" for heat-related health effects proposed thus far (e.g., Davis et al. 2003; Li et al. 2013; Pascal et al. 2006) offers considerable variability in terms of utility for heat-health adaptation strategies.

The aim of this study was to systematically identify the meteorological conditions under which there might be reasons to enact heat-health interventions based on empirical relationships between hot weather and illness or death. Our concern was that an opportunity to mitigate a large portion of adverse health outcomes associated with heat may be lost if the activation of preventive measures for heat-related illness and death is keyed to temperatures at which all-cause mortality statistically exceeds a seasonal baseline. In hot climates such as the one that characterizes Maricopa County, Arizona, health events associated with heat exposure may begin to occur well before a statistical threshold temperature for all-cause mortality is crossed (Harlan et al. …

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