According to a study by JAMA Cardiology, a monthly peer-reviewed medical journal, which analysed information on about 274,000 people living in Sweden in 2018, the risk of having a heart attack was greatest on days when the temperature was below freezing point.
PLOS One, an open-access scientific journal, in a study in 2015 found more than a 31 percent increase in heart attacks in the coldest months of the year compared with the warmest. Several studies suggest that during extremely cold conditions, the risk of getting a stroke increases by 80 percent, particularly when the temperature dips below 15 degrees Celsius.
As temperatures drop, the blood vessels tighten and blood flow speeds up to help stay warm. That is why the blood pressure is often higher in colder seasons, opines cardiologists.
"Onset of winters can evoke mixed reactions. As per some studies, the chances of a person suffering from a heart attack goes up nearly 33 percent during winters. The Coronary arteries like other arteries can constrict during winter which can lead to a poor supply of blood to the heart muscle. Decreased blood supply can precipitate myocardial ischemia and heart attack," said Tarun Kumar, Professor of Cardiology, ABVIMS and RML Hospital.
Dr Tarun said that there is increased blood volume during winters. As in summer, there is increased fluid loss through sweat which is missing in winters. It can lead to increased saltand fluid retention during winter which can lead to an increase in blood pressure and heart attacks.
"Because of hormonal variations during winters, there is an increase in levels of clotting factors including fibrinogen. Adding fuel to fire is vasoconstriction and platelet aggregability along with clotting factors, which can lead to an increased tendency for clot formation and heart attacks", he added.