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

Abstract

In general, there are few studies that analyse the impact of low temperatures on mortality, and even fewer that extend this analysis to specific causes of mortality. This study had a twofold aim: Firstly, to analyse the trend in natural-, circulatory-and respiratory-cause mortality associated with cold waves in Castile-La Mancha (Spain) across a period of analysis of 34 years, which would confer an important degree of temporal representativeness on the results obtained; and secondly, to ascertain whether this impact had decreased over the years. Time series analysis using multivariate ARIMA models with data on daily natural-, circulatory-and respiratory-cause mortality in Castile-La Mancha. The independent variables were minimum daily temperature, mean daily pressure and mean daily relative humidity. We controlled for seasonalities and trend of the series, as well as influenza epidemics, cold-wave duration and chronological number in any given year. Data were stratified in three ten-year stages, i.e. , 1975-1985, 1986-1996 and 1997-2008. The mortality trigger temperature was set at a minimum daily temperature of -2°C, corresponding to the 4th % of the minimum temperature series for the winter months considered. The impact on daily natural-cause mortality for each degree that the minimum daily temperature was below -2°C was: 10.4 % (95 % CI 9.6-11.2) in the first decade; 11.9 % (95 % CI 11.0-12.8) in the second decade; and fell to 1.6 % (95 % CI 0.9-2.3) in the third. This same pattern was observed for circulatory-and respiratory-cause mortality, with the effect of cold being greater for respiratory causes. Socio-economic factors -both of adaptation and demographic-could account for this sharp decrease in mortality associated with low temperatures. These results question climate models which predict the effects of cold over long-term time horizons, while maintaining the risk attributable to low temperatures constant. Studies similar to ours should be undertaken in other regions to confirm whether it is solely local characteristics that explain this pattern or, on the contrary, whether the pattern is generalised.

Geographical variation in relative risks associated with cold waves in Spain: The need for a cold wave prevention plan

“…Cold exposure is a trigger factor for certain diseases and can contribute to aggravation of prevailing chronic diseases (Rytkonen et al, 2005). Furthermore, the trend observed across a 34-year period of analysis in Castile-La Mancha (Spain) (Linares et al, 2015a), which in itself confers an important degree of temporal representativeness, indicates that cold waves have not been accompanied by a rise in mean winter minimum temperatures and have been constant in intensity and number of days. This is in line with other studies which, in the context of climate change, indicate there are climate models which predict that extreme cold weather events are likely to occur over continental European areas, and other middle-and high-latitude regions, under 21stcentury warming scenarios (Kodra et al, 2011).…”

“…This is in line with other studies which, in the context of climate change, indicate there are climate models which predict that extreme cold weather events are likely to occur over continental European areas, and other middle-and high-latitude regions, under 21stcentury warming scenarios (Kodra et al, 2011). There are very few studies which forecast possible cold-related impacts on the basis of climate models (Vardoulakis et al, 2014), and these assume that the impact of cold on mortality will remain constant over the envisaged prediction period and that it is temperatures that will change (Linares et al, 2015a). Moreover, there has been a shift in the cold-wave pattern, with a decrease in the month of November and a substantial increase in intensity in the month of December (Linares et al, 2015a), a finding that is in line with what has been observed elsewhere in Europe, consisting of a prolongation of summer months and a more delayed, yet more abrupt, onset of winter (Brunetti et al, 2000;WHO, 2007).…”

“…There are very few studies which forecast possible cold-related impacts on the basis of climate models (Vardoulakis et al, 2014), and these assume that the impact of cold on mortality will remain constant over the envisaged prediction period and that it is temperatures that will change (Linares et al, 2015a). Moreover, there has been a shift in the cold-wave pattern, with a decrease in the month of November and a substantial increase in intensity in the month of December (Linares et al, 2015a), a finding that is in line with what has been observed elsewhere in Europe, consisting of a prolongation of summer months and a more delayed, yet more abrupt, onset of winter (Brunetti et al, 2000;WHO, 2007). Currently, however, there are no cold prevention plans in place in the vast majority of European cities, despite the fact that these plans are more effective than heat plans in terms of preventable deaths/day.…”

Cold-related mortality vs heat-related mortality in a changing climate: A case study in Vilnius (Lithuania)

“…The percentiles in those studies were between 1 st and 3 rd . The relatively high percentile value (7 th percentile of the minimum temperatures of the winter months) in Vilnius may be related to cold acclimatisation factors and socio-economic conditions (Linares et al, 2016;. In general, cold-related mortality is associated with an increase in respiratory-cause mortality, though a relationship has been reported between low temperatures and circulatory-cause morbidity and mortality (Chau et al, 2014).…”

“…However, a reduction in the frequency, duration or intensity of cold waves may not necessarily translate into a decrease in cold-related mortality. Various studies in multiple locations suggest that while heat-related mortality is in decline due to various adaptative processes (Gasparrini et al, 2015;Mirón et al 2015;Díaz et al 2015a;Ha and Kim 2013;Petkova et al, 2014), cold-related mortality has either remained constant or increased (Gasparrini et al 2015;Díaz et al 2015a;Linares et al, 2016).…”