Objectives The impact of extreme diurnal temperature range (DTR) on cardiovascular morbidity in Mediterranean regions remains uncertain. We aimed to analyse the impact of extreme low DTR (stable temperature) or high DTR (changeable temperature) on cardiovascular hospitalisations in Catalonia (Southern Europe).
Methods We conducted a self-controlled case series study using whole-year data from the System for the Development of Research in Primary Care database and 153 weather stations from the Catalan Meteorological Service. The outcome was first emergency hospitalisation. Monthly DTR percentiles were used to define extreme DTR as low (DTR <the 5th percentile) and high (DTR>95th percentile). We assessed two effects: same-day (1-day exposure, coinciding with the extreme DTR episode) and cumulative (3-day exposure, adding two subsequent days). Incidence rate ratios (IRR) were calculated adjusted by age, season and air pollution. Stratified analyses by gender, age or cardiovascular type and regions are provided.
Results We computed 121 206 cardiovascular hospitalisations from 2006 to 2013. The IRR was 1.032 (95% CI 1.005 to 1.061) for same day and 1.024 (95% CI 1.006 to 1.042) for cumulative effects of extreme high DTR. The impact was significant for stroke and heart failure, but not for coronary heart disease. Conversely, extreme low DTR did not increase cardiovascular hospitalisations.
Conclusions Extreme high DTR increased the incidence of cardiovascular hospitalisations, but not extreme low DTR. Same-day effects of extreme high DTR were stronger than cumulative effects. These findings contribute to better understand the impact of outdoor temperature on health, and to help defining public health strategies to mitigate such impact.
- health promotion
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Contributors IP and RR conceived of the presented idea. AP and IP designed the study. DP and RM obtained data from different data sources. JB and MC-C performed the statistical analyses. DP and LA-C searched relevant bibliography. AP wrote the manuscript with support from LA-C, RML and MMG-G. All authors contributed to the interpretation of the results and approved the manuscript.
Funding This work was supported by the Daniel Bravo Private Foundation, the Agency for Management of University and Research Grants (AGAUR) and from Carlos III Health Institute of the Ministry of Economy and Competitiveness (Spain) through the Network for Prevention and Health Promotion in Primary Care (redIAPP, RD12/0005/0002), cofinanced with European Union Health Institute/European Regional Development Fund (ERDF).
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval This study has the approval of the Ethics Committee from the Jordi Gol Research Institute (IDIAPJGol) (reference: P15/105).
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement No data are available. The datasets generated during and/or analysed during the current study are not publicly available due to legal reasons related to data privacy protection. Information on how to submit an application for gaining access to SIDIAP data is available at https://www.sidiap.org/index.php?lang=en. To request access to the analyses scripts, please contact the corresponding author.