Christmas is meant to be joyful. For some, however, the holidays are more stressful than enjoyable. A recently published Swedish study featured in the British Medical Journal showed that Swedes had suffered more than 283,000 heart attacks between 1998 and 2013 during the Christmas season. The risk of a heart attack increased 15 percent on Christmas Eve, 37 percent on Christmas Day, and 20 percent on New Year’s Day.

Cardiologists warn of the dangers of stress when it comes to affecting existing heart conditions, said Meagan Murphy Wasfy, M.D., a cardiologist at Mass General Hospital in Boston.

“There’s been a lot of research showing that any kind of stressful event happening at national scale increases the risk of a heart attack,” added Christopher Kelly, M.D., a cardiologist at Columbia University Medical Center.

Even during emotional events like the World Cup, heart attacks can be aggravated. A study revealed that the risk increased considerably for many Germans whenever the national team was playing. Other stressful events that may induce a heart attack include Monday morning traffic and loud noise. Escalations in stress inflame the arteries, which can increase activity in the amygdala, a region of the brain, spurring the risk of cardiovascular disease and heart complications. “Short-term risk of heart attack is higher when experiencing stressors,” Kelly says.

At Christmas, factors like jet lag, gridlock, complicated family reunions, and overdrinking can provoke atrial fibrillation, which is known as holiday heart and is characterized by an irregular heartbeat that can cause blood clots and other heart complications, says Kelly.

Heart attacks, however, tend to affect those with pre-existing heart conditions or those who smoke, have high cholesterol, diabetes, or are overweight, which can result in plaques that cause blood clots that obstruct arterial flow. “Stress can rip the roof off of a plaque and the plaque can cause a blood clot that blocks off the artery,” Kelly says. A blocked artery will eventually lead to a heart attack, though stress can exacerbate the condition.

Still, it’s important during the holidays to enjoy ourselves and relax, as well as to learn to cope with stress and minimize binge eating and drinking. Symptoms that are cause for alarm, however, are pressure in the chest area and shortness of breath. “Anyone who has these symptoms needs to hurry up and seek medical attention,” Kelly says. “It’s a situation where every minute counts.”

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In the US, nearly a million people a year suffer heart attacks, resulting from blockage of blood flow to the heart, which prevents the heart from getting the necessary oxygen. When blood flow is blocked for extended periods of time, the heart muscle starts to die. However, those who receive immediate treatment have a greater chance of survival.