People who experience the death of a partner are at an increased risk of developing an irregular heartbeat for up to a year afterwards, a new study has found.

An irregular heartbeat, also known as atrial fibrillation (AF), can make the heart less efficient at pumping blood around the body. This can lead to symptoms such as palpitations, breathlessness and angina, and those with AF have an increased risk of suffering a stroke or heart failure.

Over 33 million people worldwide are thought to be affected, including as many as 40,000 adults over the age of 50 in Ireland.

Danish researchers looked at over 88,000 people newly diagnosed with AF and compared them to more than 886,000 healthy people between 1995 and 2014.

Almost 17,500 of the AF group and 168,940 of the comparison group had lost their partners.

The study found that those who had been bereaved had a 41% increased risk of developing AF for the first time compared to people who had not been bereaved.

These findings stood irrespective of the participants' gender or underlying conditions.

The risk of developing AF seemed to be greatest eight to 14 days after the death of a partner. After this time, it started to subside, but it was a full year before the risk was similar to that of someone who had not lost a partner.

The highest risk was found among people under the age of 60 - they were more than twice as likely to develop AF if they had lost their partner.

The risk of AF also appeared to be greater among people who had lost their partners unexpectedly. If a person was relatively healthy in the month before their death, their partner was 57% more likely to develop AF. This increased risk was not found in people whose partners were unwell and were expected to die soon.

The researchers said that while the reasons for this link are unclear, bereavement is known to increase the risk of heart disease, mental health problems and even death.

They believe that the acute stress brought about by losing a partner may disrupt normal heart rhythms and lead to the production of chemicals that cause inflammation.

"In addition, patients with AF often claim that emotional stress is a common triggering factor and increasing levels of perceived stress are associated with prevalent AF," the researchers said.

Details of these findings are published in the journal, Open Heart.