Weather data could help predict up to three days in advance when the number of out-of-hospital cardiac arrests is likely to rise above average, according to a nationwide study of more than 114,000 cases by researchers from Semmelweis University, the Budapest University of Technology and Economics, and the Hungarian National Ambulance Service.
The study, published in Public Health, found that lower temperatures emerged as one of the most important weather-related risk factors examined. In the future, models based on weather forecasts could help people with cardiovascular disease and their families prepare for higher-risk periods, while also supporting ambulance services and hospitals in managing expected increases in demand.
The researchers compared data on out-of-hospital cardiac arrests that occurred between November 2018 and December 2023 with daily meteorological indicators, including temperature, wind speed, atmospheric pressure, humidity and air quality.
Why predicting cardiac arrest cases matters
Out-of-hospital cardiac arrest (OHCA) is one of the leading causes of death in developed countries. In Europe, there are an estimated 67–170 cases per 100,000 people each year, while survival remains below 10%. Identifying factors that can predict an expected rise in case numbers could therefore help emergency medical services prepare, raise public awareness of the importance of rapid intervention and resuscitation, and, in the longer term, contribute to improving survival rates.
The analysis found that falling temperatures were among the most important weather-related risk factors for cardiac arrest: every 1°C decrease in average temperature was associated with a 1.4% increase in the daily number of out-of-hospital cardiac arrests. A seasonal comparison also showed that nearly 18% more such events occurred in winter than in summer. The findings therefore suggest that it is not only sudden drops in temperature that may pose a risk, but lower temperatures in general. Rapid changes may nevertheless be particularly important: a daily temperature drop of more than 5°C could serve as a warning signal in an early warning system.
One of the study’s key findings was that the effects of weather changes may not be immediate: the number of out-of-hospital cardiac arrests may rise up to three days later. This could make it possible to develop early warning systems capable of predicting increased demand on healthcare services several days in advance.
The researchers developed a predictive model that used meteorological data to estimate the expected daily number of out-of-hospital cardiac arrests.
The researchers not only had to determine which atmospheric parameters had the greatest influence on the number of cardiac arrests, but also how to use them to build a reliable predictive model.
The next step could be to develop an early warning system that uses weather forecasts to help ambulance services and hospitals plan capacity and manage expected increases in demand. In the future, such a system could also alert people with cardiovascular disease and their families to higher-risk periods, helping them pay closer attention to warning symptoms and seek medical attention sooner when necessary.
