London: Heart attacks are more prevalent in the winter season, as lower temperatures act as an external trigger for the life threatening condition, a study claims.
Researchers at Lund University in Sweden found that there was a higher occurrence of heart attacks in sub-zero temperatures.
When the daily temperature was less than zero degree Celsius, the average rate of heart attacks a day peaked to four, as compared to when it was above 10 degrees, researchers said.
Furthermore, occurrence of heart attacks was increased with higher wind velocities, limited sunshine duration and higher air humidity.
The findings were the same across a large range of patient subgroups, and at national as well as regional levels, suggesting that air temperature is a trigger for heart attack.
The body responds to cold by constricting superficial blood vessels, which decreases thermal conduction in the skin and subsequently increases arterial blood pressure, researchers said.
Other responses are shivering and increased heart rate, which raise the metabolic rate and in turn increase body temperature, they added.
"There is seasonal variation in the occurrence of heart attack, with incidence declining in summer and peaking in winter," Moman A Mohammad from the Department of Cardiology at Lund University.
"Our results consistently showed a higher occurrence of heart attacks in sub-zero temperatures. The findings were the same across a large range of patient subgroups, and at national as well as regional levels, suggesting that air temperature is a trigger for heart attack," Mohammed added.
Researchers studied the specific weather conditions during which heart attacks occurred using local meteorological data from hundreds of weather stations.
During the study period, a total of 280,873 heart attacks occurred of which meteorological data were available for 99 per cent.
The average number of heart attacks per day was significantly higher during colder temperatures as compared to warmer.
The results were consistent across health care regions.