Cold, cloudy weather could increase your risk of having a heart attack, according to a new study.

In the largest study of its kind, scientists examined data from more than 274,000 patients across Sweden who had heart attacks between 1998 and 2013 for which contemporary weather data was available.

The study found that the incidence of heart attacks increased with lower air temperature, lower atmospheric air pressure, higher wind velocity and shorter sunshine duration. The most pronounced association was observed for air temperature.

David Erlinge, professor of cardiology at Lund University in Sweden and leader of the study, said: “This is by far the largest study of weather and heart attacks. We are very interested in the triggers of heart attacks, because if you know those triggers you may be able to protect yourself.”

The incidence of heart attacks was higher on days with air temperatures below freezing, with rates declining significantly when temperatures rose to greater than 3-4C. The association with air temperature also held true for different types of heart attack, including the most common type, which is caused by the blockage of a major coronary artery, an important blood vessel supplying the heart.

The scientists speculate that cold weather could cause narrowing of arteries, putting extra pressure on the heart. “Cold and windy weather leads to a contraction of blood vessels in the skin to conserve energy and temperature,” said Erlinge. “That increases the workload of the heart, increasing the risk of a heart attack.”

Other possible explanations are changes in behaviour during colder weather – alterations to diet or exercise habits, for example – or the increase in respiratory infections such as flu during winter, which have been associated with increased heart attack risk.

“Cold, windy weather also increases emotional stress, which is also coupled to the incidence of heart attack,” added Erlinge.

In studying the association of various weather parameters with heart attack risk, Erlinge and his team also took into account national data on air pollution, which has recently been linked to changes in heart structure. “We looked at data on air pollution in the three major Swedish cities every day during the 16 years,” said Erlinge. “Air pollution did not change the results reported in our study.”

Chris Gale, professor of cardiovascular medicine at the University of Leeds, who was not involved in the study, said: “In the UK there are in excess of 100,000 heart attacks per year, so heart attacks are a major public Health and population burden and anything that can be done to alleviate this has got to be good.”

On the results of the study, Gale said: “There are public Health implications of this – for example, being mindful of when we are going to have a cold patch of weather so we are prepared in terms of our Health and wellbeing, making sure we are wrapped up and warm.

“Clearly if the climate is changing such that we are getting more extremes of temperature, including colder weather snaps, then this could impact adversely on heart Health.”

Previous studies have reported increases in deaths from heart disease during winter, and recent research has linked the incidence of heart attacks to colder temperatures and snow.

In the new paper, published in Jama Cardiology, the authors caution that it remains unknown whether reducing cold exposure by staying indoors and/or wearing warm clothes could reduce the risk of heart attack, and that this would need further investigation.

(THE GUARDIAN)