Image of a heart in the chest

Heart-related deaths rise during the holidays, but the cold winter season might not be to blame, according to new research in the Journal of the American Heart Association.

“Spikes in deaths from natural causes during Christmas and New Year’s Day has been previously established in the United States. However, the Christmas holiday period in the U.S. falls within the coldest period of the year when death rates are already seasonally high due to low temperatures and influenza,” said Josh Knight, study author and research fellow at the University of Melbourne in Australia.

Researchers analyzed trends in deaths in New Zealand, where Christmas is in the summer when death rates are usually at a seasonal low. This let them separate any winter effect from a holiday effect.

Researchers found a 4.2 percent increase in heart-related deaths away from a hospital from Dec. 25 to Jan. 7, from 1988 to 2013. A range of theories may explain the death spike, including emotional stress, changes in diet and alcohol consumption, less staff at medical facilities and changes in the physical environment.

Researchers suggest one possibility may be that patients hold back in seeking medical care during the holiday season. Another explanation could be terminally ill patients’ will to live and hold off death for a day that is important to them.

“The ability of individuals to modify their date of death based on dates of significance has been both confirmed and refuted in other studies. However, it remains a possible explanation for this holiday effect,” Knight said.