New research from Hungary suggests that cooling temperatures are a significant weather-related risk factor for out-of-hospital cardiac arrests (OHCA). The study, published in the journal Public Health, found that each one-degree Celsius drop in average daily temperature was associated with a 1.4% increase in the number of cardiac arrests occurring outside hospital settings.
Analysing more than 114,000 cases across Hungary between November 2018 and December 2023, researchers from Semmelweis University in Budapest, the Budapest University of Technology and Economics, and the Hungarian National Ambulance Service compared daily meteorological data—including temperature, wind speed, air pressure, humidity, and air quality—with OHCA records. Their findings reveal a clear seasonal pattern: winter months saw nearly 18% more cardiac arrests than summer.
Forecasting cardiac arrest risk
The study's authors argue that weather forecasts could be used to predict periods of elevated cardiac arrest risk up to three days in advance. This lead time could allow ambulance services and hospitals to prepare for increased demand, and help vulnerable patients and their families take precautionary measures.
“The impact of weather changes does not necessarily appear immediately,” the researchers note. “It may show up as an increase in out-of-hospital cardiac arrests as late as three days afterwards.” This delayed effect underscores the importance of monitoring temperature trends rather than just reacting to sudden cold snaps.
Rapid temperature drops appear particularly dangerous. A daily fall of more than 5°C could serve as a warning sign in an early warning system, the study suggests.
Why forecasting matters
Out-of-hospital cardiac arrest is one of the leading causes of death in developed countries. In Europe, incidence ranges from 67 to 170 cases per 100,000 inhabitants each year, with survival rates below 10%. Any tool that can signal an impending rise in cases could help emergency services allocate resources more effectively and alert the public to the importance of immediate CPR and defibrillation.
The findings add to a growing body of evidence linking environmental factors to cardiovascular health. For instance, night-time light exposure has been linked to heart damage, and even low-level air pollution can disrupt sleep, both of which may have implications for cardiac risk.
While the study is observational and cannot prove causation, the large dataset and nationwide scope lend weight to its conclusions. The researchers hope that meteorological forecast models could eventually be integrated into public health alerts, helping to reduce the burden of OHCA across Europe.
As climate change brings more variable weather patterns, understanding these links becomes increasingly important. The study offers a practical pathway: using existing weather data to protect vulnerable populations and support emergency services in their life-saving work.
