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In general, there are few studies that analyse the impact of low temperatures on mortality and fewer still that use cold-wave-definition thresholds based on epidemiological and non-climatological criteria. Such a threshold definition, which took into account population features such as socio-economic and demographic characteristics, made it possible for a specific threshold temperature to be obtained for each of Spain's 52 provincial capitals in this study. Using generalised linear models with the Poisson regression link, and controlling for trend, autocorrelations and seasonalities of the series, and influenza epidemics, we obtained the impact of low temperatures on mortality in each provincial capital by calculating the relative risks (RRs) and attributable risks (ARs) for natural as well as circulatory and respiratory causes. The study showed higher minimum temperature thresholds in coastal areas, and an overall impact of cold on mortality in Spain due to natural causes RR = 1.13 (95% CI: 1.11–1.16), circulatory causes RR = 1.18 (95% CI: 1.15–1.22) and respiratory causes RR = 1.24 (95% CI: 1.20–1.29) slightly greater than that obtained to date for heat. From a public health standpoint, there is a need for specific cold wave prevention plans at a regional level which would enable mortality attributable to low temperatures to be reduced. These plans have shown themselves to be effective in decreasing heat-related mortality, and we feel that they are essential for reducing cold-related effects on morbidity and mortality. [ABSTRACT FROM AUTHOR]

A number of studies have shown that there is a time trend towards a reduction in the effects of heat on mortality. In the case of cold, however, there is practically no research of this type and so there is no clearly defined time trend of the impact of cold on mortality. Furthermore, no other specific studies have yet analysed the time trend of the impact of both thermal extremes by age group. We analysed data on daily mortality due to natural causes (ICD-10: A00-R99) in the city of Madrid across the period 2001–2009 and calculated the impact of extreme temperatures on mortality using Poisson regression models for specific age groups. The groups of age selected coinciding with the pre-existing age-groups analyzed in previous papers. For heat waves the groups of age used were: <10 years, 10–17 years, 18–44 years, 45–64 years, 65–74 years and over-75 years. For cold waves the groups of age used were: <1 year; 1–5 years, 6–17 years, 18–44 years, 45–64 years, 65–74 years and over-75 years. <1, 1–17, 18–44, 45–66, 65–74 and over-75 years. We controlled for confounding variables, such as air pollution, noise, influenza, pollen, pressure and relative humidity, trend of the series, as well as seasonalities and autoregressive components of the series. The results of these models were compared to those obtained for the same city during the period 1986–1997 and published in different studies. Our results show a lightly reduction in the effects of heat, especially in the over-45-year age group. In the case of cold, the behaviour pattern was the opposite, with an increase in its effect. Heat adaptation and socio-economic and public-health prevention and action measures may be behind this amelioration in the effects of heat, whereas the absence of such actions in respect of low temperatures may account for the increase in the effects of cold on mortality. From a public health point of view, the implementation of cold wave prevention plans covering all age groups is thus called for. [ABSTRACT FROM AUTHOR]