Excess Mortality Associated with Utah Heat Events

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Wednesday, 7 January 2015
Randy Graham, NOAA/NWSFO, Salt Lake City, UT; and N. Hosenfeld

Extreme heat events have been correlated with increased mortality and morbidity in communities around the world, particularly those that lie in temperate regions. Although tornadoes, hurricanes and significant floods may be more dramatic and garner more attention, heat is the number one weather related killer in United States resulting in approximately 400 deaths per year (source: Centers for Disease Control and Prevention). However, mortality associated with heat is frequently underreported as extreme heat results in increased mortality above rates typical for a particular location and time of year through causes other than heat stroke and hyperthermia (e.g., cardiovascular and respiratory ailments). These are often referred to as “excess deaths”.

Numerous mortality studies have identified weather conditions during which mortality increases, although the values vary regionally (and seasonally) and such thresholds have not been established for Utah. This study utilizes mortality and weather data for the period 2002-2012 to identify meteorological thresholds at which mortality begins to increase along Utah's heavily populated Wasatch Front. The daily number of deaths will be correlated with atmospheric conditions in an effort to identify meteorological thresholds at which mortality begins to show a marked increase. County level mortality data for the state of Utah has been provided by the Utah Department of Health (UDOH) for the period of 2002-2012. The daily mortality data will be correlated with a variety of meteorological parameters including daily maximum and minimum temperatures, apparent temperature and relative humidity.

Results of multiple linear regression identifying the variables and values that best correlate with excess mortality during heat events will be presented. Additionally, polynomial best fit curves will be constructed utilizing afternoon record maximum temperatures and record overnight high minimum temperatures and correlated with mortality data to determine the utility of a simple and graphical approach that could be provided to community decision makers to help with identification of, and planning for, heat events. Most heat impacts are the same day as the extreme temperatures; however duration of the heat event is also an important consideration. To account for this potential effect, an analysis exploring the impact of time lag on mortality during multi-day heat events will also be presented.