Changes in cause-specific mortality during heat waves in central Spain, 1975–2008

Abstract

The relationship between heat waves and mortality has been widely described, but there are few studies using long daily data on specific-cause mortality. This study is undertaken in central Spain and analysing natural causes, circulatory and respiratory causes of mortality from 1975 to 2008. Time-series analysis was performed using ARIMA models, including data on specific-cause mortality and maximum and mean daily temperature and mean daily air pressure. The length of heat waves and their chronological number were analysed. Data were stratified in three decadal stages: 1975-1985, 1986-1996 and 1997-2008. Heat-related mortality was triggered by a threshold temperature of 37 °C. For each degree that the daily maximum temperature exceeded 37 °C, the percentage increase in mortality due to circulatory causes was 19.3 % (17.3-21.3) in 1975-1985, 30.3 % (28.3-32.3) in 1986-1996 and 7.3 % (6.2-8.4) in 1997-2008. The increase in respiratory cause ranged from 12.4 % (7.8-17.0) in the first period, to 16.3 % (14.1-18.4) in the second and 13.7 % (11.5-15.9) in the last. Each day of heat-wave duration explained 5.3 % (2.6-8.0) increase in respiratory mortality in the first period and 2.3 % (1.6-3.0) in the last. Decadal scale differences exist for specific-causes mortality induced by extreme heat. The impact on heat-related mortality by natural and circulatory causes increases between the first and the second period and falls significantly in the last. For respiratory causes, the increase is no reduced in the last period. These results are of particular importance for the estimation of future impacts of climate change on health.

Time trend in natural-cause, circulatory-cause and respiratory-cause mortality associated with cold waves in Spain, 1975–2008

“…On the one hand, in the first two decades the impact of cold on natural-cause mortality is similar to what has been observed for heat in this same region (Mirón et al 2014). As regards the pattern of specific-cause mortality, the impact of cold is less than that of heat for circulatory causes and greater for respiratory causes, a finding that is in line with the higher winter mortality linked to infectious respiratory-tract diseases and with the greater impact of cold on respiratory disease mortality (Ebi and Mills 2013).…”

“…Studies conducted in this same geographical area have reported that heat-related mortality also decreased over the last 30 years (Mirón et al 2014), a trend which is in line with other studies undertaken elsewhere (Ha and Kim 2013;Schifano et al 2012) but is not as marked as occurs in the case of low temperatures.…”

“…This uncertainty due to possible temporal variations in the impact of temperatures on mortality has been highlighted in studies addressing high temperatures (Ha and Kim 2013;Wu et al 2014;Linares et al 2014b), based on recent studies on time trends in the impact of heat on mortality, which talk of a lessening of such impacts over time (Mirón et al 2014;Schifano et al 2012) but not in the case of mortality associated with low temperatures. An in-depth examination of possible temporal variations in the impacts of cold on mortality would therefore appear to be called for.…”

Has there been a decrease in mortality due to heat waves in Spain? Findings from a multicity case study

“…Studies undertaken in CLM (Mirón et al 2014) and elsewhere around the world (Ha and Kim 2013) report a trend towards a decline in the impact of heat on mortality. It seems that socio-demographic and economic factors and health-service improvements might account for this effect (Mirón et al 2014). The influence of social factors is showing itself to be decisive in its relationship with other environmental variables.…”

Heat Waves' Influence on Health: Some Uncertainties about Their Impact

“…Studies conducted in different parts of the world show that, far from remaining constant, these impacts are changing over time, with a trend towards the minimisation of such effects [19], i.e., while the effect is most pronounced in cardiovascular-cause mortality [20], it has remained practically constant in the case of respiratory-cause mortality [21]. These results, obtained from a time series covering a time span of over 30 years, show that the increase in risk of heat-related mortality for each degree centigrade that the threshold temperature is exceeded, went from 13.7% in the decade 1975-1985 to 7.4 % in the decade 1997-2008, and specifically, that this decline was due to circulatory causes, going from 18.2% in the period 1975-1985 to 5.8% in the period 1997-2008; in the case of respiratory causes, however, no such decline was in evidence, with the respective figures remaining practically constant, i.e., 11.8% in 1975-1985 versus 13.5% in 1997-2008.…”