A nationwide cohort study in Denmark found that mortality rates have significantly decreased during the past three decades among patients who had an MI before they turned 50 years old.

However, their mortality rate was still approximately two times higher than the general population. The increased risk was mainly due to deaths from ischemic heart disease and other smoking-related diseases.

Lead researcher Morten Schmidt, MD, PhD, of Aarhus University Hospital in Skejby, Denmark, and colleagues published their results online in Circulation: Cardiovascular Quality and Outcomes on Aug. 30.

“Although 30-day risk of death following a heart attack has decreased markedly in the last 30 years, younger patients should still have concerns about their long-term health,” Schmidt said in a news release. “It is estimated that half of the decline in deaths from heart attacks since 1980 is attributable to primary prevention and, in particular, the reduction in the number of patients who smoke. The other half is likely attributable to a combination of things such as the introduction of early treatments that restore blood flow to the part of the heart muscle damaged during a heart attack, improvement in hospital organization, and better management of high blood pressure and high cholesterol.”

For this population-based study, the researchers used the Danish National Patient Registry and examined data from all hospitals in Denmark from 1980 to 2009. They identified 21,693 patients who were younger than 50 years old when they had their first hospital inpatient diagnosis of MI. They then examined 30-year cause-specific death rates of those patients and compared them with 216,930 sex- and age-matched people from the general population.

The median age of the patients was 45 years old, and 79.5 percent were men. The prevalence of stable angina pectoris, hypertension, diabetes and obesity was higher in the MI group than in the general population. Meanwhile, the median follow-up period was 11.4 years in the MI group and 16.6 years in the general population.

The researchers found that the 30-day mortality risk among the MI group decreased from 12.5 percent from 1980 to 1989 to 8.4 percent from 1990 to 1999 to 3.2 percent from 2000 to 2009. In addition, the 31- to 365-day mortality risk decreased from 5.1 percent to 2.3 percent to 1.6 percent, while the 1- to 10-year mortality risk decreased from 24.2 percent to 12.7 percent to 8.9 percent.

Between 1980 to 1989 and 2000 to 2009, the mortality rate ratio decreased 4.5-fold within 30 days from 468 to 97; 3-fold within 31 to 365 days from 11.32 to 3.70; and 2.5-fold within 1 to 10 years from 4.77 to 1.89. The researchers also said that patients undergoing PCI or CABG had a significant decrease in 1- to 10-year mortality risk compared with patients who did not receive an interventional treatment. Females also had a higher 1- to 10-year mortality rate ratio.

The researchers mentioned a few limitations of the study, including that the registry does not include patients who had sudden cardiac death outside of a hospital or ambulance and who do not undergo attempted resuscitation in the emergency room. They also noted that the cause of death was based on subjective clinical judgment and not an autopsy. Further, they did not have information on lifestyle factors such as smoking.

“Our data show that long-term survival after premature MI has decreased remarkably over the last 3 decades,” the researchers wrote. “The results likely apply to most industrial Western societies in which changes in lifestyle, risk factor modification, and healthcare systems have followed international recommendations. Still, MI patients should be advised that an excess risk of fatal events persists, warranting adherence to prescribed medical therapy and efforts to reduce modifiable lifestyle-related risk factors, particularly smoking.”