Heart attack happens when the flow of oxygen-rich blood to an area of the heart is blocked.
When the heart muscle cannot get enough oxygen, it begins to die very quickly, and thus immediate treatment is very important.
One common cause of heart attacks is coronary heart disease, in which plaque builds up inside of the coronary arteries and causes blood clot.
Heart attacks have lots of risk factors, and many are related to bad lifestyle behaviors.
An unhealthy diet, lack of physical activity, smoking, being overweight or obese are linked to higher risk of a heart attack.
Some chronic health conditions, like high blood pressure, high blood sugar and high blood cholesterol are big risk factors of heart attacks.
There are also some risk factors people cannot control, such as aging, family history of heart disease, and high blood pressure during pregnancy (preeclampsia).
Recently, scientists from Lund University find that air temperature can be an external trigger of heart attacks.
The study examined more than 280,000 patients across 16 years. They find there is seasonal variation in the ratio of heart attack.
In summer heart attack occurs less while in winter heart attacks happens more frequently.
The researchers studied the specific weather conditions during which heart attacks occurred using local meteorological data from hundreds of weather stations from 1 Jan 1998 to 31 Dec 2013.
The patient health data is from Swedish myocardial infarction registry. All heart attacks were treated at a coronary care unit.
The team found that the average number of heart attacks every day was much higher during colder temperatures as compared to warmer temperatures. The results were consistent across healthcare regions.
Specifically, under 0°C, there were four more heart attacks every day compared to above 10°C. The occurrence of heart attacks was increased with higher wind velocities, limited sunshine duration and higher air humidity.
Even after the effects of high blood pressure, aging, type 2 diabetes, previous heart attacks and medication use were removed, the link between air temperature and heart attack incidence was still found.
The researchers said “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”.
Why is the air temperature associated with heart attacks?
The researchers explained that the body responds to cold by constricting superficial blood vessels.
This can decrease thermal conduction in the skin and subsequently increases arterial blood pressure.
Other responses are shivering and increased heart rate, which raise the metabolic rate and in turn increase body temperature.
For healthy people these mechanisms can work fine and are well tolerated. But for some people who have plaque in their arteries, the mechanism can trigger a heart attack.
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