Being in good shape may improve a person's chances of surviving a first heart attack, a new study indicates.

"We knew that fitter people generally live longer, but we now have evidence linking fitness to survival after a first heart attack," said study author Dr. Michael Blaha. He is a heart specialist and assistant professor of medicine at the Johns Hopkins University School of Medicine in Baltimore.

"It makes sense, but we believe this is the first time there is documentation of that association," Blaha said in a Hopkins news release.

The study also adds to evidence that regular exercise reduces the risk of heart attack and death from all causes, he said.

The researchers examined the medical records of more than 2,000 people, average age 62, who had done a treadmill stress test before they suffered a first heart attack. The tests provide a metabolic equivalent (MET) score, which ranges from 1 to 12, with 12 being the most physically fit.

Those with MET scores of 10 or higher were 40 percent less likely to die after a first heart attack than other patients. And one-third of patients with a MET score of 6 or less died within a year of their first heart attack, the study found.

Overall, each whole number increase in MET score was associated with an 8 percent lower risk of death after a first heart attack, according to the researchers from Johns Hopkins and the Henry Ford Health System in Detroit.

However, only an association was seen between MET scores and risk of death after a first heart attack, not a cause-and-effect connection.

Study author Clinton Brawner, a clinical exercise physiologist at the Henry Ford Health System, said, "Our data suggest that doctors working with patients who have cardiovascular risk factors should be saying, 'Mr. Jones, you need to start an exercise program now to improve your fitness and chances of survival, should you experience a heart attack.' "

Each year, about 550,000 people in the United States have a first-time heart attack, according to the American Heart Association.

The new study was published online Feb. 1 in the journal Mayo Clinic Proceedings.