A type of irregular heartbeat that greatly increases the risk for stroke develops much earlier in men, a new study shows.

Atrial fibrillation causes the upper chambers of the heart to quiver. Left untreated, it increases the risk of heart-related death and is linked to a five-fold increased risk of stroke.

The findings, published Monday in Circulation, show men develop the condition about a decade earlier than women on average, and being overweight is a major risk factor. Researchers also found that AFib more than tripled the risk of dying.

“It’s crucial to better understand modifiable risk factors of atrial fibrillation,” said study author Christina Magnussen, M.D., an internal medicine and cardiology specialist at the University Heart Center in Hamburg, Germany.

“If prevention strategies succeed in targeting these risk factors, we expect a noticeable decline in new-onset atrial fibrillation,” leading to less illness, fewer deaths and lower health-related costs, she said.

Researchers reviewed records of nearly 80,000 people ages 24 to 97 who took part in four European studies. The participants were followed for up to 28 years.

Ultimately, 4.4 percent of women and 6.4 percent of men had been diagnosed with AFib. Diagnosis rates jumped when men were 50 or older and women were 60 or older. In addition, 31 percent of men with a higher body mass index developed the condition compared with 18 percent of women with a higher BMI.

“We advise weight reduction for both men and women,” Magnussen said. “As elevated body mass index seems to be more detrimental for men, weight control seems to be essential, particularly in overweight and obese men.”

Researchers said it is unclear what factors might be causing sex differences in AFib risk.

Since participants were from northern and southern Europe, the findings likely apply to other Caucasian populations but cannot be generalized to other racial and ethnic groups, Magnussen said. However, since BMI was such a strong risk factor for AFib, it is likely applicable to other groups, she added.

Between 2.7 and 6 million Americans have atrial fibrillation, and more than 12 million are expected to have the condition in 2030, according to American Heart Association statistics.

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