A type of irregular heartbeat that is a major risk factor for stroke develops much earlier in men, the results of a new study suggest.

Atrial fibrillation (AF) causes irregular and rapid heartbeats, which can make the heart less efficient at pumping blood around the body. This can lead to palpitations, breathlessness, dizziness, angina and the development of blood clots. However, there may be no symptoms, therefore a person may be unaware that they have it.

AF affects up to 40,000 people over the age of 50 in Ireland and those with the condition are five times more likely to suffer a stroke.

Now, a new German study has found that men develop this condition, on average, about a decade earlier than women, and being overweight is a major risk factor.

Researchers studied the medical records of almost 80,000 people aged between 24 and 97 who took part in four different studies in Europe. All of the participants were followed for an average of 12 years.

The study found that diagnosis rates for AF jumped when men were 50 or older and when women were 60 or older.

Among both men and women with a higher body mass index (BMI), new AF cases increased more in men - 31% in men compared to 18% in women.

"It's crucial to better understand modifiable risk factors of AF. If prevention strategies succeed in targeting these risk factors, we expect a noticeable decline in new-onset AF.

"We advise weight reduction for both men and women. As elevated BMI seems to be more detrimental for men, weight control seems to be essential, particularly in overweight and obese men," commented study author, Dr Christina Magnussen, of the University Heart Center in Hamburg.

The researchers said that since the study's participants were from both northern and southern Europe, the findings probably apply to other Caucasian populations, but should not be generalised to other groups.

However, they added that since BMI was such a strong risk factor for AF in the study, it is likely to also have an impact on other groups.

Details of these findings are published in the journal, Circulation.