TUESDAY, Nov. 11 (HealthDay News) -- Three decades of a pronounced reduction in risk factors for heart disease is slowing considerably.

In fact, Mayo Clinic researchers report that the trend has flattened, starting at the beginning of the millennium.

"Dramatic declines in risk scores date back a fair amount of time, but now they're leveling off," said Dr. Russell V. Luepker, Mayo professor of epidemiology and community health at the University of Minnesota, in Minneapolis. "We've seen this in Minnesota as well, but this is national data. Progress we have been making in a number of areas is less clear because of the obesity epidemic. Things are not improving as much."

The researchers, presenting their findings Tuesday at the American Heart Association's annual scientific sessions in New Orleans, said this was the first time national data had been analyzed in this way.

"This was a definite surprise for those who spend their lives, as I do, trying to prevent heart disease," said study author and cardiologist Dr. Francisco Lopez-Jimenez. "We think that it is due to a combination of the obesity epidemic and also the factors that make people obese... like suboptimal diet, limited exercise and eating a lot of salt. Salt is not necessarily related to obesity, but it is related to blood pressure."

"The first step is to recognize that we have significant shortcomings and big challenges ahead of us," Lopez-Jimenez said.

Heart disease risk had been declining with gains in lowering cholesterol and blood pressure, as well as victories in helping people quit smoking.

According to the study authors, that trend started to change around 2000.

An analysis of national data revealed that the average age-adjusted 10-year risk for cardiovascular disease decreased from 10 percent to 7.9 percent from the period 1976-1980 to the period 1988-1994.

But that the risk decreased to a much lesser extent between 1988-1994 and 1999-2004, from 7.9 percent to 7.4 percent, only a half-percent decline.

This was true in all age groups except older individuals. And the trend seemed most pronounced in women.

The study didn't address why this might be so, but Luepker said the University of Minnesota is seeing some interesting trends on campus.

The university has seen increases in smoking rates among freshman, especially young women who want to avoid gaining the infamous "Freshman 15," Luepker said.

But the university health service has come up with an initiative to combat food intake and weight gain without cigarettes: They eliminated trays from the cafeterias.

The disposable containers "can only carry so much food," Luepker stated. And the University of Minnesota food service is now reporting a lower intake of food.

More information

The American Heart Association has more on risk factors for coronary heart disease.