A large U.S. study that followed middle-aged men and women for about 25 years found that those who stuck most closely to a list of seven heart-healthy practices were over 60 percent less likely to develop atrial fibrillation than those who met few or none of the list's criteria.

Atrial fibrillation is the most common heart rhythm disorder in the U.S., affecting about 2 million people, the study authors note in the Journal of the American Heart Association.

"A heart rhythm disorder is something where your heartbeat is not beating regularly, so whenever your heartbeat is not beating regularly, it's called an arrhythmia. That's a big deal, because this arrhythmia, if untreated, can lead to stroke," lead author Dr. Parveen Garg said in a telephone interview.

"We know that atrial fibrillation is a growing disease . . . and unlike other cardiovascular diseases, it's not something that we've really targeted to try and prevent," said Garg, a cardiologist with the Keck School of Medicine at the University of Southern California in Los Angeles.

To see if an existing prevention strategy for heart disease overall would also influence who develops atrial fibrillation, the study team analyzed data on 13,182 people and calculated their "Life's Simple 7" scores.

This tool, developed by the American Heart Association, awards one point for performing well with regard to each of seven modifiable risk factors for heart disease: smoking, body mass index (BMI), physical activity, diet, blood pressure, total cholesterol and fasting blood glucose.

Participants' average age was 54 and they were free of heart disease when the study started in the 1980s. Half were followed for at least 25 years, with periodic physical testing and surveys that researchers used to track adherence to the Life's Simple 7 principles.

Over time, 2,266 people, or 17 percent, developed atrial fibrillation.

Compared with individuals with the lowest scores, those with average scores were 41 percent less likely to develop heart rhythm problems and people with optimal scores had 62 percent lower risk. Each additional point translated to a 17 percent lowering of risk for atrial fibrillation, the researchers calculated.

“We all know that being in perfect or ideal cardiovascular health is really hard and even in our study, I think there was only 3 percent of individuals who actually had ideal health,” Garg said.

"To ask a patient who might be 50, or 60, to ask them to have perfect control of their blood pressure, and be in perfect physical shape, and have an ideal diet, that might be a bit of a stretch," he added. "But, small improvements in . . . your health might go a long way, potentially, in reducing your risk of developing this arrhythmia."

This "very timely" study shows how risk factor modification, by attacking multiple risk factors simultaneously, can have a significant impact on the development of atrial fibrillation, said Dr. Dawood Darbar, a cardiologist at the University of Illinois in Chicago and coauthor of an editorial accompanying the study.

"It’s the most common abnormal heart rhythm that cardiologists see and is one of the most common causes of stroke, particularly in the elderly, and of heart failure," Darbar said in a telephone interview, adding that atrial fibrillation is a huge burden on healthcare expenditure in the U.S. and worldwide.

More research is needed, but the large, long-term studies typically needed to prove that risk factor modification will reduce the risk of atrial fibrillation are incredibly expensive, he noted.

"So what we suggested in the editorial was that perhaps (researchers) could actually use electronic medical records to do these large studies. First, identify the individuals who may be at high risk of developing atrial fibrillation, intervene at an early stage and then look at the outcomes," Darbar said.