A standard blood test can reveal if someone is at high risk of having a heart attack within six months, a new study shows.

Researchers identified dozens of biomarkers in blood linked to the risk of a first heart attack, according to a report published Monday in the journal Nature Cardiovascular Research.

"The samples that are already taken in healthcare now are enough to predict the risk" of an impending heart attack, said lead researcher Johan Sundstrom, a cardiologist and professor of epidemiology at Uppsala University in Sweden.

Heart attacks are the most common cause of death. However, it's been difficult to predict heart attacks because most known risk factors exist in a person long before they have their emergency, researchers said.

"We know that the time just before a heart attack is very dynamic," Sundstrom said in a university news release. "For example, the risk of a heart attack doubles during the month after a divorce, and the risk of a fatal heart event is five times as high during the week after a cancer diagnosis."

Given that, researchers analyzed blood samples taken from 420 people at least six months before they suffered their first heart attack. They compared those results to nearly 1,600 healthy people.

"We identified around 90 molecules that were linked to a risk of a first heart attack," Sundstrom said. "We wanted to develop methods that would enable the health services to identify people who will soon suffer their first heart attack."

These included 48 proteins and 43 biochemicals produced through metabolism, results show. Those combined with age, sex, and blood pressure were associated with the risk of an imminent first heart attack.

Using that information, researchers also created a simple online tool through which anyone can learn their risk of having a heart attack within the next half year.

The tool at miscore.org predicts heart attack risk based on age, gender, education, height, waist circumference, cholesterol levels, smoking status, and whether or not a person has diabetes.

"If you find out that you happen to have an increased risk of suffering a heart attack soon, perhaps you will feel more motivated to prevent it," Sundstrom said. "We hope that this will increase people's motivation to take their preventive medicine or stop smoking, for example."

Researchers now will study the 90 biomarkers to understand them better and see if they present any opportunities for treatment to prevent a impending heart attack, they said.