A new study reveals annual spikes in heart attack risks on Christmas eve and certain midsummer holidays, with risks peaking at 10 p.m. on Christmas eve.

What causes the risk increase?

Heart Attack Risks

For a new study, researchers analyzed data on the 283,014 heart attacks reported to Swedish hospitals from 1998 and 2013 and found that certain holidays actually increased heart attack risks. Specifically, researchers observed 15 percent higher risks on Christmas/New Year's compared to a normal December day, with the highest risks observed on Christmas eve at 10 p.m. with a whopping 37 percent increase.

Researchers also found increases in heart attack risks on Mondays, New Year’s day, and a big holiday in Sweden called the Midsummer holidays. Interestingly, they also observed generally higher heart attack risks in the early mornings, which is quite the opposite of the 10 p.m. peak on Christmas Eve.

The risks were found to be the greatest among individuals over 75 years old as well as in those with existing diabetes or heart disease. No increases were found during Easter holiday or sporting events.

Stress, Excessive Eating, And Drinking

So what is causing the increased heart attack risks on those occasions? The study alone cannot pinpoint a cause and effect relationship, but it’s possible that the excessive eating and drinking, stress, and possible long-distance travel related to those holidays may be key contributors.

For instance, Christmas eve is actually the main day of Christmas celebrations in Sweden, and it is the day when families gather together. In the case of the midsummer holiday, it is considered the most important holiday in Sweden following Christmas and is often celebrated by dancing around a maypole, singing, and often excessive eating and drinking. Excessive merrymaking is also associated with New Year’s celebrations.

As such, it is possible that the indulgences related to those holidays may be a trigger to the heart attacks, as observed in the Christmas eve reversal of the year-round pattern of higher heart attack risks in the early mornings.

Vulnerable Individuals

The results of the study are actually in line with previous studies that link holidays with increased risks for heart attacks. As such, experts are urging members of the public to be more vigilant during the holiday season, especially for peers or family members who are more vulnerable to heart attacks.

The study is published in the BMJ.