‘BIG’ women are at a nearly three-fold greater risk of suffering from an irregular heartbeat than their shorter and lighter counterparts, new research warns.
A 30-year study involving 1.5million females showed that taller and heavier women - though not necessarily fat - are at more risk from the potentially fatal problem than smaller ones.
Irregular heartbeat, atrial fibrillation, is the most common heart rhythm disorder.
It occurs most often in people over the age of 60 and increases the risk of stroke and heart failure.
Lead researcher Professor Annika Rosengren, of Gothenburg University in Sweden, said: "Our research has previously shown that a large body size at age 20, and weight gain from age 20 to midlife, both independently increase the risk of atrial fibrillation in men.
"In this study we investigated the impact of body size on atrial fibrillation risk in women."
The study analysed data on the women’s weight, height, age, diabetes, hypertension and smoking over a period of up to 33 years.
They were divided into four groups according to their body surface area - calculated by a standard formula based on weight and height.
Professor Rosengren said: "We found that bigger women have a greater risk of atrial fibrillation.
"There was a stepwise elevation in risk with increasing body size. The group with the highest body surface area had nearly three times the risk as those with the lowest body surface area."
BSA is influenced by both height and weight. Compared to women with the lowest BSA, those with the highest BSA were 3.5ins taller, 61.7lbs heavier and had a higher body mass index.
Professor Rosengren said: "Atrial fibrillation is the result of obesity-related metabolic changes but there is also a second cause.
"Big people - not necessarily fat, but big - have a larger atrium, which is where atrial fibrillation comes from. People with a bigger atrium have a higher risk of atrial fibrillation.
"Generally it's better to be tall because you have less risk of stroke and heart attack, and better survival. Taller people are often are better educated, have higher socioeconomic status, and may have received better nutrition at a young age and in the womb.
"But in this case being tall is less desirable because it alters the structure of the heart in a way that may be conducive to atrial fibrillation."
Professor Rosengren pointed out that the absolute risk of atrial fibrillation in these young women, regardless of weight, height or BSA was very low at less than 0.5 per cent.
She said: "In general young women need not worry about their risk of atrial fibrillation, whatever their body size.
"For older women and men, being big could be an indicator that you are at increased risk of atrial fibrillation. In the clinic I have seen many big people with atrial fibrillation."
She added: "If you are very tall, I think that it could be a good idea to avoid accumulating excess weight. That would apply to both men and women."
The findings are due to be presented at the Prevention, Epidemiology and Population Science conference in Malaga, Spain.