In the U.S., preventable risk factors still account for 50 percent of deaths from cardiovascular disease among adults age 45 to 79, according to a new analysis.

But even if every state brought levels of those risk factors – such as obesity and smoking - down to the best level any state has so far achieved, less than 10 percent of heart disease deaths would be prevented, the researchers estimated.

Unexpectedly, “there wasn’t a huge difference” in cardiovascular-related deaths “between best off and worst off states,” said lead author Shivani A. Patel of the Rollins School of Public Health at Emory University in Atlanta, Georgia.

Although the death toll has steadily declined over the past 30 years due to prevention and treatment measures, heart disease is still the leading cause of death in the U.S., causing one in every four deaths, or 610,000 deaths each year, according to the Centers for Disease Control and Prevention.

To estimate how many heart disease deaths are due to preventable factors, Patel and her coauthors analyzed responses from more than 500,000 people, ages 45 to 79, to a landline phone-based behavioral risk factor survey in 2009 and 2010, as well as data from the National Health and Nutrition Examination Survey.

The researchers write in Annals of Internal Medicine that had it been possible to completely eliminate every case of high cholesterol, high blood pressure, diabetes, obesity and smoking in the U.S., 54 percent of heart disease deaths among men and almost 50 percent of heart disease deaths among women in 2010 could have been prevented.

They also estimated, in a more feasible scenario, that if all states could have brought the levels of those five risk factors down to the levels achieved by the five best-performing states in the U.S., that would have prevented about five percent of heart disease deaths.

“Even the best states aren’t doing that well,” Patel said.

High blood pressure and smoking were tied to the highest proportion of preventable deaths.

In 2009 and 2010, the states with the lowest levels of risk factors were in the West, like Colorado, and those with the highest levels were in the South, including Kentucky, West Virginia, Mississippi, Alabama and Louisiana.

About 80 percent of people reported exposure to at least one of the five risk factors.

“By the time they’re in this age range what we’re seeing is it doesn’t matter what state you’re in, you’re very likely to have at least one of these risk factors,” Patel said.

Risk factors cluster, so many Americans actually have more than one risk factor, said Dr. Blair J. O'Neill of Alberta Health Services in Canada, who was not part of the U.S. study.

“Although not measured in this study, risk factors are more prevalent in poorer, less well educated populations, likely accounting for the greater burden in Southern and Midwestern states,” O’Neill told Reuters Health by email.

But great progress has been made in reducing cardiovascular disease and death since the 1960’s, he said.

“Tobacco legislation has helped tremendously through taxation levels sufficient enough to reduce adolescent smoking,” he said. “Healthy food availability in schools and workplaces improves nutrition. Mandatory salt and trans-fat reductions in food also has reduced hypertension and cholesterol levels.”

“I think the message is that there is still room for improvement,” Gabriela Vazquez Benitez of HealthPartners Institute for Education and Research in Minneapolis, Minnesota, told Reuters Health by email.

Smoking is on the decline, and obesity and diabetes may soon become the number one risk factors for cardiovascular disease, Patel said.

Health care providers should work to not only treat these risk factors, but also prevent them by intervening with patients at an early age, she said.