[Effects of temperature extremes on daily mortality in Castile-La Mancha (Spain): trends from 1975 to 2003]

Changes in the temperature-mortality relationship in France: Limited evidence of adaptation to a new climate

CONTEXT

Documenting trends in the health impacts of ambient temperature is key to supporting adaptation strategies to climate change. This paper explores changes in the temperature-related mortality in 18 French urban centers between 1970 and 2015.

METHOD

A multicentric time-series design with time-varying distributed lag nonlinear models was adopted to model the shape of the relationship and assess temporal changes in risks and impacts.

RESULTS

The general shape of the temperature-mortality relationship did not change over time, except for an increasing risk at very low percentiles and a decreasing risk at very high percentiles. The relative risk at the 99.9^th percentile compared to the 50^th percentile of the 1970-2015 temperature distribution decreased from 2.33 [95% confidence interval (CI): 1.95:2.79] in 1975 to 1.33 [95% CI: 1.14:1.55] in 2015. Between 1970 and 2015, 302,456 [95% CI: 292,723:311,392] deaths were attributable to non-optimal temperatures, corresponding to 5.5% [95% CI: 5.3:5.6] of total mortality. This burden decreased progressively, representing 7.2% [95% CI: 6.7:7.7] of total mortality in the 1970s to 3.4% [95% CI: 3.2:3.6] in the 2000s. However, the contribution of hot temperatures to this burden (higher than the 90^th percentile) increased.

DISCUSSION

Despite the decreasing relative risk, the fraction of mortality attributable to extreme heat increased between 1970 and 2015, thus highlighting the need for proactive adaptation.

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

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.

Mortality on extreme heat days using official thresholds in Spain: a multi-city time series analysis

Background

The 2003 heat wave had a high impact on mortality in Europe, which made necessary to develop heat health watch warning systems. In Spain this was carried-out by the Ministry of Health in 2004, being based on exceeding of city-specific simultaneous thresholds of minimum and maximum daily temperatures. The aim of this study is to assess effectiveness of the official thresholds established by the Ministry of Health for each provincial capital city, by quantifying and comparing the short-term effects of above-threshold days on total daily mortality.

Methods

Total daily mortality and minimum and maximum temperatures for the 52 capitals of province in Spain were collected during summer months (June to September) for the study period 1995-2004. Data was analysed using GEE for Poisson regression. Relative Risk (RR) of total daily mortality was quantified for the current day of official thresholds exceeded.

Results

The number of days in which the thresholds were exceeded show great inconsistency, with provinces with great number of exceeded days adjacent to provinces that did not exceed or rarely exceeded. The average overall excess risk of dying during an extreme heat day was about 25% (RR = 1.24; 95% confidence interval (CI) = [1.19-1.30]). Relative risks showed a significant heterogeneity between cities (I² = 54.9%). Western situation and low mean summer temperatures were associated with higher relative risks, suggesting thresholds may have been set too high in these areas.

Conclusions

This study confirmed that extreme heat days have a considerable impact on total daily mortality in Spain. Official thresholds gave consistent relative risk in the large capital cities. However, in some other cities thresholds

Influence of local factors in the relationship between mortality and heat waves: Castile-La Mancha (1975-2003)

INTRODUCTION

All the climate-change studies undertaken to date agree that one of the principal consequences of this phenomenon is the increase in heat waves, which, without exception, are linked to marked rises in mortality. The characteristics that modulate and determine the relationship between high temperatures and health must therefore be ascertained in the greatest possible detail, so that really effective prevention plans can be designed to address temperature extremes.

METHODS

We examined the effect of heat waves on daily non-accidental-cause mortality across all age groups in the Castile-La Mancha region (Spain) from 1975 to 2003. Quantitative analyses were performed using autoregressive integrated moving average (ARIMA) models, with other covariates, such as pressure trends, relative humidity, and duration and chronological number of heat waves.

RESULTS

Mortality increased significantly with respect to the mean, when temperatures exceeded the designated provincial thresholds in Castile-La Mancha. For each degree centigrade that temperatures exceeded these thresholds, the percentage increase in mortality amounted to increases of approximately 12% over the daily mean, albeit with clear provincial variations. The longest heat waves were associated with daily mortality, with those at the end of summer causing the lowest mortality. Meteorological situations most closely associated with increases in mortality were cyclonic conditions accompanied by low humidity.

CONCLUSIONS

Spatio-temporal variability in the temperature-mortality relationship must be studied in order to enable really effective heat-wave prevention plans to be drawn up. The influence of variables, such as heat-wave duration or time of appearance, is important in the total increase in mortality during temperature extremes. Since parameters, such as humidity or pressure trends, can play very different roles in different geographical settings, they should be analysed separately from temperature.

Intense cold and mortality in Castile-La Mancha (Spain): study of mortality trigger thresholds from 1975 to 2003

Studies on temperature-mortality time trends especially address heat, so that any contribution on the subject of cold is necessarily of interest. This study describes the modification of the lagged effects of cold on mortality in Castile-La Mancha from 1975 to 2003, with the novelty of also approaching this aspect in terms of mortality trigger thresholds. Cross-correlation functions (CCFs) were thus established with 15 lags, after application of ARIMA models to the mortality data and minimum daily temperatures (from November to March), and the results for the periods 1975-1984, 1985-1994 and 1995-2003 were then compared. In addition, daily mortality residuals for the periods 1975-1989 and 1990-2003 were related to minimum temperatures grouped in 2°C intervals, with a cold threshold temperature being obtained in cases where such residuals increased significantly (p < 0.05) with respect to the mean for the study period. A cold-related mortality trigger threshold of -3°C was obtained for Ciudad Real for the period 1990-2003. The significant number of lags (p < 0.05) in the CCFs declined every 10 years in Toledo (5-2-0), Cuenca (4-2-0), Albacete (4-3-0) and Ciudad Real (3-2-1). This meant that, while the trend in cold-related mortality trigger thresholds in the region could not be ascertained, it was possible to establish a reduction in the lagged effects of cold on mortality, attributable to the improvement in socio-economic conditions over the study period. Evidence was shown of the effects of cold on mortality, a finding that renders the adoption of preventive measures advisable in any case where intense cold is forecast.

Mortality from cold waves in Castile--La Mancha, Spain

INTRODUCTION

As is known, the effects of extreme temperatures on mortality are characterised by an annual periodicity, with a rise centred in the winter months. The most recent epidemiological studies show that mortality caused by cold waves is, in many cases, comparable to that caused by the severest heat waves. This study sought to quantify the rise in mortality due to extreme cold and the factors that determine the relationship between these variables in Castile-La Mancha (Spain).

METHODS

We examined the effect of extreme winter temperature on daily non accidental cause mortality in Castile - La Mancha from 1975 to 2003, for all ages. Quantitative analyses were performed using ARIMA models, with other covariates, such as influenza, pressure trends, relative humidity, and cold wave duration and chronological number.

RESULTS

There were two mortality peaks: a short-term peak (with a lag of 3 to 7 days); and a longer term peak (of under two weeks). Excess mortality during cold waves was around 10% per degree centigrade below the threshold temperature for all the provinces except Guadalajara, where an increase of only 4.61% was detected. Mortality increased in response to rises in cold-wave duration and relative humidity. Cold waves occurring at the end of the "winter" season caused the greatest mortality.

CONCLUSIONS

This study confirms that daily mortality in Castile - La Mancha increases during cold waves. Efficient cold-wave prevention plans must therefore be implemented. Such plans should be based on in-depth knowledge of the causes that underlie and modulate the relationship between low temperatures and health effects.