Cold temperatures – external trigger for seasonal variation in the occurrences of heart attacks
A study, which lasted 16 years and covered over 280,000 patients in Sweden, investigated the weather conditions during which heart attacks occurred. The study was led by Prof David Erlinge from the Swedish Lund University.
The research found the average number of daily heart attacks was much higher during colder temperatures. This meant 4 more heart attacks per day when the average temperature was less than 0 °C as compared to when it was above 10°C. This made investigators conclude that air temperature is a trigger for heart attack.
When it is cold the body constricts the superficial blood vessels which increases arterial blood pressure. To raise body temperature the organism increases the heart and metabolic rates. In spite of the fact that there might have been other reasons behind the infarctions, in the cold weather people with atherosclerotic plaques in their coronary arteries might suffer a heart attack.
Another study which examined the effects of temperature on the risk of heart attacks in Winnipeg, Canada, (700,000 inhabitants) also showed that the cold weather poses a higher risk. University of Manitoba researchers reviewed the ST-elevation myocardial infarctions (STEMI) in the city over the last 6 years. Later they juxtaposed these incidents with the average temperature of the days prior to the infarctions.
During the period there were 1,817 infarctions. On days with a daily high less than 0 °C, STEMI event rates were 0.94 per day, compared to 0.78 per day when the daily high was greater than 0 °C.