Rochester, MN - The US is heading for an epidemic of atrial fibrillation (AF), according to a new study [1]. The analysis of the incidence of AF over a 20-year period shows that twice as many people are affected as previously thought. If the increase in incidence observed over this time continues, there could be as many as 16 million with AF by 2050, say the researchers.

There is an urgent need to establish primary-prevention strategies for AF, Dr Yoko Miyasaka (Mayo Clinic, Rochester, MN) and colleagues stress in their paper published online July 3, 2006 in Circulation.

Senior author Dr Teresa Tsang (Mayo Clinic) told heartwire that the new research is unique because it provides data on the incidence of AF and trends from recent years in a general population. Previous studies have reported trends in AF incidence, but these were in specific populations and the results were conflicting, she notes.

Miyasaka et al investigated trends in the age-adjusted incidence of AF in Olmsted County, Minnesota, from 1980 to 2000. A total of 4618 adults developed first-documented AF during this time, which required ECG confirmation and verification that the episode was the first recognized AF event for that person.

The age- and sex-adjusted incidence of AF per 1000 person-years was 3.04 in 1980 and 3.68 in 2000. The incidence of AF increased significantly, with a relative increase of 12.6% over 21 years (p=0.014), they note.

"We found a significant increase in the number of people who newly developed this rhythm problem over the past two decades in Olmsted County, and this increase was not just because people were living longer," Tsang says.

She also notes that they saw no difference between men and women in this study, "which is interesting, because we always thought men were at higher risk for AF."

The incidence rates seen compare closely with those reported by the Framingham Heart Study and the Cardiovascular Health Study and with work done in other countries, including Canada and the UK, she adds.

Her team did three calculations using US Census Bureau Data—one assuming the rate of incidence of AF continues as is, one assuming that it plateaus, and a final one predicting what would happen if there was a downward trend (which Tsang stressed to heartwire is highly unlikely).

If there is a plateau in incidence, the number of people with AF is projected to be 12.1 million by 2050, the researchers say. But if the increase continues at the rate found in their study, they predict that 15.9 million people will be affected by 2050. Tsang adds that even this figure "may be an underestimation. . . . We simply cannot determine the number of persons who have silent AF that was undetected."

Tsang goes on to explain that although AF is treatable and some of the potential complications are preventable, "the overriding goal for the clinical and societal perspective should be one of primary prevention."

The reasons for the increase in AF are undoubtedly multifactorial, with hypertension, diabetes, heart failure, myocardial infarction, and valvular heart disease all regarded as risk factors for AF, she adds.

Although obesity as a risk factor has been controversial in the past, recent Framingham data convincingly suggest an important risk relationship between body-mass index and AF development, she notes. "We believe that obesity could have accounted for up to 60% of the anticipated increase in age- and sex-adjusted AF incidence in this new study."

To this end, she and her team are now specifically studying whether there is a relationship between obesity and AF, she told heartwire.

"There is also a body of work that gives us greater insight into detecting those at higher risk of AF," she explains. For example, noninvasive echo imaging can be used to identify people with increased left atrial size and those with left ventricular diastolic dysfunction; both these conditions lead to increased risk of AF.

Also required is increased public awareness of AF, aggressive intervention, and primary prevention of reversible risk factors, she notes. "We need to prevent the first episode of AF and the risk factors contributing to its development if we are to turn the tide of this growing epidemic."