Weather forecasts could help predict an increased chance of a heart attack up to three days in advance, according to researchers who examined the effects of temperature change on health. The team identified falling temperatures as one of "the most important" weather-related risk factors for out-of-hospital cardiac arrest.
Study of 114,000 people links cold to cardiac arrests
The study, involving more than 114,000 people, found that when temperatures were lower, the number of out-of-hospital cardiac arrests was likely to rise above average. Researchers from Semmelweis University, the Budapest University of Technology and Economics, and the Hungarian National Ambulance Service carried out the analysis, which was published in Public Health.
The study compared data on out-of-hospital cardiac arrests that occurred between November 2018 and December 2023. Daily meteorological indicators, including temperature, wind speed, atmospheric pressure, humidity and air quality, were examined.
1.4% increase per degree drop
The analysis found that 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 happened in winter than in summer.
Researchers said the findings "therefore suggest that it is not only sudden drops in temperature that may pose a risk, but lower temperatures in general." They added that a daily temperature drop of more than 5°C could serve as a warning signal in an early warning system.
Effects may appear up to three days later
One of the study's key findings was that the effects of weather changes may not be immediate. The researchers found the number of out-of-hospital cardiac arrests may rise up to three days later, which could make it possible to develop early warning systems capable of predicting increased demand on healthcare services several days in advance.
Dr Endre Zima, Professor at the Heart and Vascular Center of Semmelweis University and lead researcher of the study, said: "In a previous study, we examined how extreme cold and heat affect the incidence of out-of-hospital cardiac arrest. This time, we went one step further and investigated whether weather patterns could be used to predict when higher-than-average numbers of cases are likely to occur. If this proves feasible, ambulance services and hospitals could prepare for increased demand several days in advance."
Predictive model for ambulance services
The researchers developed a predictive model that used meteorological data to estimate the expected daily number of out-of-hospital cardiac arrests. Dr Ádám Pál-Jakab, resident physician and PhD student at the Heart and Vascular Center of Semmelweis University and first author of the study, said: "By combining meteorological and ambulance service data, the model could predict one to three days in advance when the number of out-of-hospital cardiac arrests is likely to rise above average. It does not estimate an individual's risk, but rather the number of cases expected nationwide."
The team said 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.
