U.S. death rates for heart disease and stroke have dropped by about 30 percent since 1999, according to the latest American Heart Association statistics.The improvement comes even though more Americans are sedentary and obese than ever before, experts noted.

“Our work isn’t done, since the major risk factors for heart disease and stroke have not seen the same declines as the death rates, and several [risk factors] are rising,” AHA President Dr. Timothy Gardner said in an association news release.

Still, between 1999 and 2006 there was a 30.7 percent decline in coronary heart disease deaths and a 29.2 percent drop in stroke deaths.

The findings were published online Dec. 15 in the AHA journal Circulation.

Despite the recent drop, cardiovascular conditions such as heart attacks and stroke remain the leading cause of death in the United States, accounting for 34.2 percent of the more than 2.4 million deaths reported in 2006.

And statistics for Americans with heart risk factors remain static. For example, while average cholesterol levels for men 40 and older and women 60 and older dropped from 204 mg/dL to 199 mg/dL between 1999 and 2006, little change was seen for other age groups, the AHA report noted.

Most Americans aren’t exercising, either. Nearly two-thirds (62 percent) of adults reported no vigorous daily activity lasting at least 10 minutes in the 2006 National Health Interview Survey. That exercise threshold is the minimum recommendation for heart-strengthening exercise.

And yet the AHA says it has still met its goal of reducing coronary heart disease and stroke by 25 percent by 2010.

How did this happen? One expert said it’s not entirely clear, but advances in medicine might take the lion’s share of the credit.

“We can speculate which aspects of cardiology have created the most improvements,” said Dr. Suzanne Steinbaum, director of women and heart disease at Lenox Hill Hospital in New York City. “Some interventions have proved to be considerably effective.”

She cited stents, the tiny flexible tubes inserted routinely after artery-opening procedures to keep vessels open. Steinbaum also mentioned implanted defibrillators and pacemakers. “All of cardiology has been improving,” she said.

Yet the new report also foreshadows future problems, she noted. For example, it is now possible to measure coronary artery calcification — deposits that can thicken to block arteries. One U.S. study found that 15 percent of men ages 33 to 45 and 5.1 percent of women of the same age already had significant artery calcification, making them more likely to have cardiovascular problems in the years ahead.

America’s children aren’t in the best shape, either, Steinbaum said. She said there’s already been talk of giving cholesterol-reducing statin drugs to young people.

“We might not see any immediate change in the death rate, but we might start seeing a change in incidence,” she said. “What concerns me most of all is that we might start seeing an increase in heart disease in young people.”

The incidence of overweight (body mass index at the 95th percentile) increased among children 6 to 11 years of age from 4 percent in 1971-74 to 17 percent in 2003-2006, the new report said. Among infants from 6 months to 23 months of age, the prevalence of high weight-for-age was 7.2 percent in 1976-1980 and 11.5 percent in 2003-2006.

It all cycles back to lifestyles, Gardner said.

“The challenge we face with reducing risk factors is figuring out what motivates people to change behavior, narrowing the gaps in gender and socioeconomic disparities, and assessing what we can do on a broad scale to affect the environments where people live, work and play,” he said.

(Source: Suzanne Steinbaum, M.D., director of women and heart disease, Lenox Hill Hospital, New York City; Dec. 15, 2008, news release, American Heart Association; Dec. 15, 2008, Circulation)