Comparison of UTCI with Other Thermal Indices in the Assessment of Heat and Cold Effects on Cardiovascular Mortality in the Czech Republic

Aleš Urban,Jan Kyselý

doi:10.3390/ijerph110100952

Abstract

We compare the recently developed Universal Thermal Climate Index (UTCI) with other thermal indices in analysing heat- and cold-related effects on cardiovascular (CVD) mortality in two different (urban and rural) regions in the Czech Republic during the 16-year period from 1994–2009. Excess mortality is represented by the number of deaths above expected daily values, the latter being adjusted for long-term changes, annual and weekly cycles, and epidemics of influenza/acute respiratory infections. Air temperature, UTCI, Apparent Temperature (AT) and Physiologically Equivalent Temperature (PET) are applied to identify days with heat and cold stress. We found similar heat effects on CVD mortality for air temperature and the examined thermal indices. Responses of CVD mortality to cold effects as characterised by different indices were much more varied. Particularly important is the finding that air temperature provides a weak cold effect in comparison with the thermal indices in both regions, so its application—still widespread in epidemiological studies—may underestimate the magnitude of cold-related mortality. These findings are important when possible climate change effects on heat- and cold-related mortality are estimated. AT and PET appear to be more universal predictors of heat- and cold- related mortality than UTCI when both urban and rural environments are of concern. UTCI tends to select windy rather than freezing days in winter, though these show little effect on mortality in the urban population. By contrast, significant cold-related mortality in the rural region if UTCI is used shows potential for UTCI to become a useful tool in cold exposure assessments.

Highlights

An adverse effect of heat and cold stress on mortality due to cardiovascular diseases has been reported in many studies [1]
Physiologically Equivalent Temperature (PET) and Apparent Temperature (AT) fit well with Universal Thermal Climate Index (UTCI) (the coefficient of determination (R2) is around 0.93, and there are about 83% warm days in common for these pairs of indices in both regions), the AT calculation does not include the effect of Tmrt
We investigated the ability of UTCI and other thermal indices to identify discomfort days having adverse effects on patients with cardiovascular diseases (CVD) in two regions of the Czech Republic

Summary

Introduction

An adverse effect of heat and cold stress on mortality due to cardiovascular diseases has been reported in many studies [1] Most of these employed air temperature or another simple measure of equivalent temperature (empirical indices) including effects of air temperature, humidity and/or wind speed (apparent temperature, heat index etc., [2]). Human thermal comfort is an outcome of energy balance between the human body surface and the environment, and it is influenced by human physiology, psychology and behaviour [3,4] Not all of these factors are well characterized by empirical indices, which, are unable to serve all human-biometeorological applications (e.g., public weather service, public health system, urban and regional planning, climate impact in the health sector) across all climatic zones, regions and seasons [4]. Human thermal comfort indices such as Physiologically Equivalent Temperature (PET [6,7,8]) based on the Munich Energy—Balance Model for Individuals (MEMI) and the Klima–Michel model with

Results

Discussion

Conclusion