Fatty food, extra wine and annoying relatives may be causing a spike in heart attacks over Christmas.

University of Melbourne researchers analysed 25 years of death records in the southern hemisphere between Christmas and the first week of January.

They found heart-related deaths in hospital rose by 4.2 per cent during the Christmas season in New Zealand.

Heart attack levels rose by 4.2 per cent over Christmas, a study of death records going back 25 years found

Fatty food is a contributing factor to Christmas heart attacks, the research found. (Stock image)

The report, published in the Journal of the American Heart Association, explored whether changes in diet, more alcohol and visiting relatives were to blame.

Lead author Josh Knight, a researcher at the University of Melbourne's Centre for Health Policy, said delays in seeking medical help were also contributing factors.

'The Christmas holiday period is a common time for travel within New Zealand, with people frequently holidaying away from their main medical facilities,' he said.

'This could contribute to delays in both seeking treatment, due to a lack of familiarity with nearby medical facilities, and due to geographic isolation from appropriate medical care in emergency situations.'

The prospect of spending time with annoying relatives isn't a help if you have a weak heart. (Stock image)

People who are gravely ill may be delaying treatment to have gravy with their loved ones

Terminally-ill people may also be trying to hold off dying so they could spend Christmas with their loved ones.

'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,' Mr Knight said.

Previous research in the United States found heart attacks rose during Christmas, which coincides with winter in the northern hemisphere when mortality rates are higher.

The researchers don't mince their words: fatty food isn't healthy during Christmas

Heart attacks at Christmas time are a much more serious issue than a food coma after lunch. (Stock image)

The University of Melbourne researchers set out to investigate if non-weather related factors caused heart attack levels to rise during the Christmas season.