Colder Weather May Trigger Heart Attacks

The peak incidence of ST-Segment Elevation Myocardial infarction (STEMI) that occurs in winter suggests that temperature may be the trigger, claims a new study.

Researchers at Skåne University Hospital (Lund, Sweden), Karolinska Institutet (KI; Solna, Sweden), and other institutes collected data from the Swedish Meteorological and Hydrological Institute (SMHI) for all cities with a coronary care unit reporting to the Swedish nationwide coronary care registry. All STEMI events from 1998 to 2013 were included and linked to the SMHI database on date of symptom onset and city. Average daily minimum temperature was then calculated and stratified as below 0°C, 1–10°C, and above 10°C, and the relationship between average STEMI/day and average minimum air temperature was evaluated.

The results showed that 124,042 STEMI events occurred during the study period, with meteorological data available for 96% of the patients. The average number of STEMI/day was higher during colder temperatures as compared to warmer; at temperatures of <0°C, there were a mean of 21.25 heart attacks; at temperatures of 1–10°C, there were a mean 20.83 heart attacks; and at temperature above 10°C, there were a mean 19.21 heart attacks.

The results translate into an extra four heart attacks per day in Sweden when the average daily temperature is less than 0 °C, as compared to when it was above 10°C. The researcher also found that the occurrence rate of heart attacks increased with higher wind velocities, limited sunshine duration, and higher air humidity. Consistent results were observed in both STEMI and non-STEMI cardiac events. The study was presented at the European Society of Cardiology (ESC) annual conference, held during August 2017 in Barcelona (Spain).

“There is seasonal variation in the occurrence of heart attack, with incidence declining in summer and peaking in winter; it is unclear whether this is due to colder temperatures or behavioral changes,” said lead author Moman Mohammad, MD, of the department of cardiology, who added that other factors may have contributed to the results. “Respiratory tract infections and influenza are known risk factors for heart attack that have a clear seasonal variation. In addition, seasonal-dependent behaviors such as reduced physical activity and dietary changes could play a role in the increased occurrence of heart attack during colder weather.”

Related Links:
Skåne University Hospital
Karolinska Institutet