Heart attacks are affecting a new group of Americans, a new study is reporting.

According to researchers who examined heart disease risk factors in more than 3,900 patients who were treated at Cleveland Clinic from 1995 to 2014, cases that involved the most severe type of heart attack had occurred in younger and fatter adults who were more likely to have many preventable risk factors, which included smoking status, high blood pressure (hypertension) and type 2 diabetes.

The researchers reported that the average age of a patient who had a ST-elevation myocardial infarction (STEMI) fell from 64 to 60, while the percentage of patients who could be classified as obese increased from 31 to 40 percent. A STEMI heart attack happens when plaque buildup blocks a main artery in the heart.

The rates for the other risk factors also increased significantly. The proportion of patients with diabetes, hypertension and chronic obstructive pulmonary disease (COPD) increased from 24 to 31 percent, 55 to 77 percent and 5 to 12 percent, respectively.

For smoking rates, the researchers were surprised to find an increase, especially since the national smoking rate has been on the decline over the past two decades. The percentage of patients who were smokers increased from 28 to 46 percent.

The researchers' findings reiterate the importance of making lifestyle changes that can help lower heart disease risk.

"On the whole, the medical community has done an outstanding job of improving treatments for heart disease, but this study shows that we have to do better on the prevention side," said Samir Kapadia, professor of medicine and section head for interventional cardiology at Cleveland Clinic. "When people come for routine checkups, it is critical to stress the importance of reducing risk factors through weight reduction, eating a healthy diet and being physically active."

Kapadia added, "Prevention must be kept in the forefront of primary care. Cardiac health is not just dependent on the cardiologist. The primary care physicians and the patient need to take ownership of this problem."

Vice President of the American College of Cardiology (ACC) Dr. Mary Norine Walsh stated that the study's findings are concerning, especially since programs aimed to reduce people's risk factors have been successful in the broader population. Walsh added that larger studies that involve more patients are needed to see if this study's findings will hold true.

The study's findings will be presented at the ACC's 65th Annual Scientific Session in April.