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Introduction and objectives Episodes of extreme heat are associated with increased morbidity and mortality in chronically-ill patients but there is a need to clearly establish the relationship between extreme heat and myocardial infarction. The aim of this study was to analyze the relationship between the incidence of ST-segment elevation myocardial infarction (STEMI) and maximum temperature, in particular during heat wave alert periods (HWAP). Methods The population studied consisted of confirmed STEMI cases registered in the Infarction Code of the Community of Madrid between June 2013 and June 2017. Incidence rate ratios (IRR) adjusted for trend and seasonality and 95%CI were estimated using time series regression models. Results A total of 6465 cases of STEMI were included; 212 cases occurred during the 66-day period of HWAP and 1816 cases during the nonalert summer period (IRR, 1.14; 95%CI, 0.96-1.35). The minimum incidence rate was observed at the maximum temperature of 18 °C. Warmer temperatures were not associated with a higher incidence (IRR,1.03; 95%CI, 0.76-1.41), whereas colder temperatures were significantly associated with an increased risk (IRR, 1.25; 95%CI, 1.02-1.54). No effect modification was observed by age or sex. Conclusions We did not find an increased risk of STEMI during the 66 days of HWAP in the Community of Madrid between June 2013 and June 2017. However, an increased risk was found during colder temperatures. No extra health resources for STEMI management are required during periods of extreme heat, but should be considered during periods of cold weather. Resumen Introducción y objetivos Los episodios de calor extremo se asocian con una mayor morbimortalidad de los enfermos crónicos, pero su relación con el infarto de miocardio no está claramente establecida. El objetivo es analizar una posible relación entre la incidencia de infarto agudo de miocardio con elevación del segmento ST (IAMCEST) y la temperatura máxima, especialmente durante los periodos de alerta por ola de calor (PAOC). Métodos La población estudiada son los casos de IAMCEST confirmado registrados en Código Infarto Madrid entre junio de 2013 y junio de 2017. Se estimaron las razones de tasa de incidencia (RTI) ajustadas por tendencia y estacionalidad y sus IC95% asociadas con los PAOC y con la temperatura máxima, utilizando modelos de regresión de series temporales. Resultados Se incluyó a 6.465 casos de IAMCEST. En 66 días de PAOC hubo 212 casos y 1.816 casos durante los días de verano sin alerta (RTI = 1,14; IC95%, 0,96-1,35). La tasa de incidencia mínima se observó con temperatura máxima de 18 °C. Las temperaturas más cálidas no se asociaron con mayor incidencia (RTI = 1,03; IC95%, 0,76-1,41); por el contrario, hubo un incremento significativo con las temperaturas más frías (RTI = 1,25; IC95%, 1,02-1,54). No hubo modificación por sexo o edad. Conclusiones Durante los PAOC entre junio de 2013 y junio de 2017 en la Comunidad de Madrid, no se observó un aumento de la incidencia de IAMCEST, pero sí durante periodos de bajas temperaturas. No cabe esperar un mayor uso de los recursos sanitarios para el IAMCEST en periodos de calor extremo, pero sí durante los periodos fríos., A. Tobías received support from the Japanese Society for the Promotion of the Science (JSPS) in its grant invitation program for research in Japan (S18149).

BackgroundPrevious studies investigating the relationship of influenza with acute myocardial infarction (AMI) have not distinguished between AMI types 1 and 2. Influenza and cold temperature can explain the increased incidence of AMI during winter but, because they are closely related in temperate regions, their relative contribution is unknown. Methods and ResultsThe temporal relationship between incidence rates of AMI with demonstrated culprit plaque (type 1 AMI) from the regional primary angioplasty network and influenza, adjusted for ambient temperature, was studied in Madrid region (Spain) during 5 influenza seasons (from June 2013 to June 2018). A time‐series analysis with quasi‐Poisson regression models and distributed lag‐nonlinear models was used. The incidence rate of type 1 AMI according to influenza vaccination status was also explored. A total of 8240 cases of confirmed type 1 AMI were recorded. The overall risk ratio (RR) of type 1 AMI during epidemic periods, adjusted for year, month, and temperature, was 1.23 (95% CI, 1.03–1.47). An increase of weekly influenza rate of 50 cases per 100 000 inhabitants resulted in an RR for type 1 AMI of 1.16 (95% CI, 1.09–1.23) during the same week, disappearing 1 week after. When adjusted for influenza, a decrease of 1ºC in the minimum temperature resulted in an increase of 2.5% type 1 AMI. Influenza vaccination was associated with a decreased risk of type 1 AMI in subjects aged 60 to 64 years (RR, 0.58; 95% CI, 0.47–0.71) and ≥65 years (RR, 0.53; 95% CI, 0.49–0.57). ConclusionsInfluenza and cold temperature were both independently associated with an increased risk of type 1 AMI, whereas vaccination was associated with a reduced risk among older patients., This work has been partially funded by unrestricted research grants from the Fundación para la Investigación Biomédica, University Hospital “Príncipe de Asturias” (Servicio Madrileño de Salud, Madrid, Spain) (to Drs García‐Lledó and de Abajo) and funding from Sanofi‐Pasteur S.A., a manufacturer of influenza vaccines (to Dr de Abajo). The funders had no role in the study design, data collection, data analysis, data interpretation, or writing the report. Dr Tobías received support from the Japanese Society for the Promotion of Science in its invitation‐to‐research fellowship program in Japan (S18149).