Know Your Odds for Heart Failure

MONDAY June 8, 2009 -- Avoiding four key risk factors -- overweight, smoking, hypertension and diabetes -- can go a long way to keeping you safe from a major killer, heart failure.

So finds new research based on data from the landmark Framingham Heart Study. Another study, also published June 9 in the online edition of Circulation, outlines a new means of predicting a person's 30-year odds of developing heart failure.

Heart failure affects an estimated 5 million Americans and is involved in 300,000 deaths each year in the United States, according to the American Heart Association.

It's not news that excess weight, smoking, high blood pressure and diabetes can all raise heart failure risk, said Dr. Ramachandran S. Vasan, a senior investigator at the Framingham Heart Study and professor of medicine at Boston University, who co-authored the two studies. But the depth of the research offered here is new, he said.

The look back at Framingham statistics, for example, "goes back over 16 years. This long duration of follow-up provides a far more robust analysis," Vasan said.

The Framingham effort began with an examination of more than 4,200 Framingham residents in the 1970s, whose average age was then 45. Vasan and his team then added in data on the children of the original participants. Follow-up exams were done every four years to see how closely the four risk factors correlated with a progressive thickening of the heart's left ventricle, a blood-pumping chamber. This gradual thickening of heart muscle contributes greatly to heart failure.

The 16-year analysis found that women had a greater and steeper rate of left ventricular thickening, and thus a higher risk of heart failure, than men. It also showed a very close relationship between the four risk factors and a thickening of the heart chamber wall.

In fact, "people with fewer risk factors had almost no increase in left ventricular mass with age," Vasan noted. "People who had more risk factors had a steeper increase in left ventricular mass with age."

Another advance, outlined in the second study, is a kind of "calculator" that allows for longer-term assessment of a young patient's odds for heart failure, said Michael J. Pencina, associate professor of biostatistics at Boston University, and a co-author of the report with Vasan.

"Until now, risk prediction and risk assessment are based on 10-year and shorter periods," Pencina said. "We are proposing a 30-year risk calculator. It will be a useful development for people aged 20 to 30 who want a fuller picture of what is happening to them."

The calculator, which will be made available through the American Heart Association, will allow most people to determine where they stand, compared both to the population at large and to the ideal, Pencina said.

"We give an optimal profile and also a normal profile," he said. "The normal profile is not quite within the recommended guidelines, but what we see in the general population. If the individual profile exceeds the optimal or normal profile, the individual should contact a physician and talk about the risk factors, what levels they should be at, and whether the physician might recommend lifestyle or other interventions."

Alongside those reports, the American Heart Association issued two scientific advisory statements for people at high risk of heart failure.

One of them was aimed at people with type 2 diabetes. According to the AHA, these individuals should perform at least two-and-a-half hours of moderate-intensity exercise or one-and-a-half hours of vigorous aerobic exercise each week, plus weight training.

The second advisory warned against use of just the body mass index (BMI) to determine obesity. BMI, which is weight in kilograms divided by height in meters squared, is a common clinical measure of weight, with overweight defined as a BMI over 25 and obesity as a BMI over 30. By those measures, one-third of Americans are overweight or obese.

The problem with BMI is that it is "a simplistic measure," said Dr. Cora E. Lewis, professor of medicine and public health at the University of Alabama at Birmingham, lead author of the advisory. "It really is telling you about the total mass of the body. It can't tell you which part is fat and which is lean, and it can't tell you where the fat is located."

Waist circumference can be a good measure of obesity risk, Lewis said, with fat around the middle being the worst. "Studies show that a person with an apple shape has a greater risk than someone who looks like a pear," she explained.

Physical activity, dieting and other measures to reduce body fat are especially important for people with diabetes, Lewis added.

More information

There's more on heart failure at the American Heart Association.

Posted: June 2009


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