Incidence of Myocardial Infarction Found to Increase With Cold Weather

Frozen thermometer, winter, weather
Frozen thermometer, winter, weather
The influence of weather on the incidence of myocardial infarction was examined.

A higher incidence of myocardial infarction (MI) was observed during days with low air temperature, low atmospheric air pressure, high wind velocity, and shorter sunshine duration, according to an observational study published in JAMA Cardiology.

Previous research has shown seasonal influence on cardiovascular mortality, linking MI to colder temperatures and snow. Researchers sought to examine whether certain meteorological conditions beyond air temperature and snow modulate the incidence of MI.

Study investigators considered seasonal day-to-day weather patterns and incidence of MI using data from a national weather service and a nationwide cardiovascular database in Sweden. All patients admitted to any coronary care unit in Sweden because of MI were included. Weather data were available for 274,029 patients (97.6%), the final study population.

Sixteen years of MI data and weather parameters were examined (January 1998 through December 2013). Data on air temperature, minimum air temperature, maximum air temperature, wind, sunshine duration, atmospheric air pressure, air humidity, snow, and rain were extracted from the weather database. Both ST-elevation MI (STEMI) and non–ST-elevation MI (NSTEMI) were considered.

Primary analysis examined air temperature with regard to total number of MIs. The secondary analyses took into consideration other weather variables with regard to the total number of MIs, STEMI, and NSTEMI.

A total of 92,044 patients were diagnosed as having STEMI. The mean age was 71.7 years, with patients with STEMI being slightly younger. Incidence of MI increased with lower air temperature, lower atmospheric air pressure, higher wind velocity, and shorter sunshine duration. The strongest association was observed for air temperature, with a higher incidence of MI on days with air temperatures colder than 0°C; rates of MI declined when temperatures rose to greater than 3°C to 4°C. Data from the study suggest that weather is independently associated with the incidence of MI but also that the association may differ with regard to season and electrocardiographic subtypes.

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Study limitations include the fact that results for meteorological variables with local effects, such as precipitation, must be interpreted cautiously. The effect estimates were also modest for the study results. The authors concluded that low atmospheric air pressure, high wind velocity, and shorter sunshine duration were associated with risk of MI, with the most evident association observed with air temperature.


Mohammad MA, Koul S, Rylance R, et al. Association of weather with day-to-day incidence of myocardial infarction: a SWEDEHEART nationwide observational study [published online October 24, 2018]. JAMA Cardiol. doi:10.1001/jamacardio.2018.3466