People who experience the most severe type of heart attack have become younger and more obese in the past two decades, according to a new study.

This group is also increasingly more likely to smoke, and to have high blood pressure and diabetes, all of which are preventable risk factors for a heart attack, the researchers found.

"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," study co-author Dr. Samir Kapadia, an interventional cardiologist at Cleveland Clinic, said in a statement.

In the study, the researchers looked at risk factors for heart disease among more than 3,900 patients who were treated for the most severe and deadly type of heart attack — called ST-elevation myocardial infarction, or STEMI — between 1995 and 2014.

This type of heart attack occurs when one of the heart's main arteries is completely blocked by plaque, which stops the flow of blood. If the person experiencing the attack receives medical attention right away, the chances of survival increase, but overall, STEMI carries a high risk of death and disability.

The researchers divided the records of the heart attack patients collected over the 20 years into four groups, each representing a span of five years.

They found that between the first five-year span and the last five-year span, the average age of patients who had had STEMI decreased from 64 to 60, while the prevalence of obesity among the patients increased from 31 to 40 percent.

They also found that the percentage of the heart attack patients who had diabetes increased from 24 to 31 percent, and the percentage of patients with high blood pressure increased from 55 to 77 percent over the same period.

Moreover, the proportion of heart attack patients who smoked increased from 28 to 46 percent. And the proportion of patients with three or more risk factors for this type of heart attack –which is a general measure of their health –increased from 65 to 85 percent.