Heat- and cold-related cardiovascular mortality and morbidity in urban and rural populations in the Czech Republic

Several studies have examined relationships of high and low air temperatures to excess cardiovascular mortality in the Czech Republic (central Europe). Much less attention has been devoted to application of thermal indices in evaluating heat- and cold-related mortality in this region. The present study compares differences in the impacts of warm and cold days on excess deaths and hospital admissions for cardiovascular diseases (CVDs) among urban (Prague) and rural population (southern Bohemia) over the 1994–2009 period. These differences are compared between selected population groups (men and women; <65 and 65+ years). Values of the 90% (10%) percentile of daily mean air temperature, Apparent Temperature (AT), Physiologically Equivalent Temperature (PET) and Universal Thermal Climate Index (UTCI) in summer (winter) were used for the definition of warm (cold) days for each region separately. Excess mortality/morbidity is represented by the number of deaths/hospital admissions above expected daily values, the latter being adjusted for long-term changes, annual and weekly cycles, and epidemics of influenza/acute respiratory infections.

Generally higher relative excess CVD mortality on warm days was identified in Prague, while for cold days we found higher excess mortality in the rural region of southern Bohemia. In contrast to mortality, excess CVD morbidity was not observed on either warm or cold days. While heat stress increases mortality especially due to chronic CVDs, the effects of cold stress are most pronounced on acute CVDs (myocardial infarction). We found air temperature, as the most widely used proxy for ambient thermal conditions in environmental epidemiology, comparable to thermal indices in assessing heat-related mortality. On the other hand, air temperature provides a weak cold effect in comparison with the thermal indices in both regions and its application 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.