ClimaPulse: Impact of heat on cardiovascular health in France: identifying temporal trends

Cardiovascular diseases are the second leading cause of death in France, and the leading cause among women. They are also a major cause of morbidity, hospitalization, and disability. However, a proportion of these diseases could be prevented by addressing modifiable risk factors, particularly environmental exposures exacerbated by climate change, such as heat. Through various physiological mechanisms, heat can affect the cardiovascular system and contribute to cardiovascular diseases. Although the harmful effect of heat on cardiovascular diseases and related mortality is well recognized, many questions remain. In France, no study has explored the effect of heat on the different causes of cardiovascular morbidity, nor its temporal evolution and determinants, or identified the populations most vulnerable to these effects.

The objectives of the project are to:

• study the effects of different heat definitions on several indicators of cardiovascular diseases and identify the populations most vulnerable to these effects;
• analyze the temporal evolution of the dose–response relationship between heat and cardiovascular diseases, as well as the determinants of these changes;
• and quantify the number of cardiovascular diseases attributable to heat and their changes over time.

This project will be based on data from the French National Health Data System (Système National des Données de Santé) from 2013 to 2023. The health events studied will include emergency department visits, hospitalizations, and deaths due to cardiovascular causes, identified according to the primary diagnoses of the International Classification of Diseases, 10th Revision (ICD-10). Daily averages of maximum, minimum, and daytime temperatures in degrees Celsius (°C) will be provided by Météo-France for each French municipality.

Various epidemiological methods will be used, including time-series analyses to identify dose–response relationships between heat and cardiovascular diseases, machine learning approaches to identify the most vulnerable populations, Bayesian hierarchical models to analyze temporal trends, and attributable risk fractions to estimate the annual number of cardiovascular diseases attributable to heat.

This project aims to improve understanding of the impact of heat on cardiovascular health over time, identify the most vulnerable populations, and analyze the determinants of changes in the relationship between heat and cardiovascular diseases. These findings will help strengthen surveillance systems and guide prevention plans, as well as long-term adaptation strategies to limit the impact of heat on cardiovascular health in France.