The number of Americans who die from heart disease has dropped. Findings of a new federal government study have revealed that heart disease-related mortality in the U.S. has declined over the past 40 years albeit not all parts of the country show similar downward trend.

The researchers of the study, which was published in the journal Circulation on March 22, also said that the hotbeds for heart diseases in the country have shifted from the Northeast to the South.

For the study, the researchers looked at the data on heart disease deaths collected between 1973 and 2010 from more than 3,000 counties of 48 contiguous states and found that each county saw a drop in heart disease death.

The average drop seen across the U.S was 61 percent but the decline widely varies. Some counties experienced a drop between 64 and 83 percent while others only saw a 9 percent decline. The counties with the smallest improvements were concentrated in Mississippi, Alabama, Arkansas, Oklahoma, Louisiana, and some parts of Texas.

Study researcher Michele Casper, an epidemiologist at the CDC, said that they have observed a north to south shift over a short period of time. She said that the findings of their study can be used by counties and communities to determine the local factors that influence heart disease rates.

Casper pointed out that based on other studies, the socioeconomic conditions of counties can impact the rates of smoking and obesity, as well as access to healthy food, which are known to affect risks for heart disease.

While Americans can lower their risks by engaging in regular exercise, eating a healthy diet and not smoking, they still need help to do these things.

"It really takes a collective effort," Casper said. "People need access to healthy food and safe places to exercise."

Despite the drop in deaths since the 1970s, heart disease, which refers to a number of conditions such as coronary artery disease that can cause heart attack, is still the No. 1 cause of death in the U.S.

Figures from the U.S. Centers for Disease Control and Prevention (CDC) show that heart disease is responsible for more than 600,000 deaths per year.