ORIGINAL ARTICLE J. Dı´az ® A. Jorda´n ® R. Garcı´a ® C. Lo´ pez J.C. Alberdi ® E. Herna´ndez ® A. Otero Heat waves in Madrid 1986–1997: effects on the health of the elderly Received: 16 March 2001 /Accepted: 21 September 2001 / Published online: 9 November 2001 Ó Springer-Verlag 2001 Abstract Objective: The objective of this paper is to analyse and quantify the effects exerted on summer mortality by extremes of heat, particularly among persons aged 65–74 and 75 years and over, groups in which mortality is higher. Methods: The study included the period from 1 January 1986 to 31 December 1997, for all people aged over 65 years resident in Madrid, based on mortality due to all causes except accidents (ICD-9 codes 1–799), and circulatory (390–459) and respiratory (460–487) causes. Meteorological variables analysed were: daily maximum temperature, daily min- imum temperature and relative humidity. To control the effect of air pollution on mortality we considered the daily mean values of sulphur dioxide (SO 2 ), total sus- pended particulate (TSP), nitric oxides (NO x ), nitrogen dioxide (NO 2 ) and tropospheric ozone (O 3 ). Univariate and multivariate ARIMA models were used. Box-Jen- kins pre-whitening was performed. Results: The results yielded by this study indicate a mortality increase up to 28.4% for every degree the temperature rises above 36.5 °C, with particular effect in women over the age of 75 years and circulatory-cause mortality. The first heat wave that leads to the greatest effects on mortality, due to the higher number of susceptible people and the duration of the heat wave, show an exponential growth in mortality. Furthermore, low relative humidity enhances the effects of high temperature, linking dryness to air pollutants, ozone in particular. Conclusions: Since a warmer climate is predicted in the future, the incidence of heat wave should increase, and more comprehensive measures, both medical and social, should be adopted to prevent the effects of extreme heat on the population, particularly the elderly. Keywords Heat waves ® Mortality ® Elderly Introduction A number of studies conducted in the Madrid Autono- mous Region have analysed seasonal daily mortality patterns with reference to a series of environmental variables, the most relevant of which proved to be those of a meteorological nature, temperature in particular [2, 26]. The above-mentioned studies found that in the case of Madrid there was a V-shaped functional relationship between the variables of temperature and mortality, akin to that observed for other places where similar climatic conditions prevail [5, 21, 31]. Analysis of the causes of mortality underlying this relationship showed that, whereas excess winter mortality was principally due to respiratory and cardiovascular diseases, excess summer mortality was fundamentally due to cardiovascular diseases [1, 29]. It would seem that the seasonal varia- tions observed in blood pressure, fibrinogens and lipids [30, 36, 39, 40] might explain the relationship between temperature and cardiovascular-disease mortality, particularly at higher latitudes [11]. While the observed temperature-mortality relation- ships may not be exclusive to our region, what is dif- ferent is the importance of the peak of excess summer mortality peculiar to regions with marked extremes of heat [13, 22, 23]. Of course, there may well be environ- mental factors at work, other than temperature, that contribute to such excess summer mortality [19, 32, 33]. Nevertheless, the importance of the phenomenon is clear, with some authors [18] ranking these so-called heat waves as the leading cause of death due to natural disasters. Moreover, there are studies which have Int Arch Occup Environ Health (2002) 75: 163–170 DOI 10.1007/s00420-001-0290-4 J. Dı´az (&) ® A. Jorda´n ® C. Lo´ pez J.C. Alberdi ® A. Otero Centro Universitario de Salud Pu´blica de Madrid, C/ General Oraa 39, 28034 Madrid, Spain E-mail: julio.diaz@uam.es Tel.: +34-1-5619602 Fax: +34-1-4116696 R. Garcı´a ® E. Herna´ndez Departamento de Fı´sica del Aire, Facultad de Ciencias Fı´sicas, Universidad Complutense de Madrid, Madrid, Spain