Adults who were physically active before suffering an MI were more likely to survive the event compared with those who were not physically active, according to a prospective cohort study.

However, the rates of subsequent heart failure or mortality were similar whether or not the adults were physically active.

Lead researcher Hanne Ejllersen, MD, of the University of Copenhagen in Denmark, and colleagues published their results online in the European Journal of Preventive Cardiology on April 11.

“Patients who were sedentary were more likely to die when they got a myocardial infarction and patients who did exercise were more likely to survive,” study author Eva Prescott, MD, of the University of Copenhagen, said in a news release. “There was also a dose-response relationship, so that the odds of dying if people got a myocardial infarction declined with the level of exercise they did, reaching an almost 50 percent reduction for those who were the most physically active.”

The researchers noted that previous studies found that regular physical activity was associated with a reduced risk of ischemic heart disease and mortality.

For this analysis, they examined 14,223 participants from the Copenhagen City Heart Study, which enrolled adults who were 20 to 93 years old from 1976 to 1978. The participants filled out a questionnaire on their general health, diseases, lifestyle and family history of coronary heart disease. They also underwent a clinical examination and non-fasting blood tests.

Participants self-reported their leisure time physical activity using a questionnaire and were grouped into four categories: sedentary (less than two hours of light physical activity per week); light (two to four hours of physical activity such as walking, cycling or light gardening); moderate (more than four hours per week of light physical activity or two to four hours of more vigorous physical activity such as brisk walking or fast cycling); and high (vigorous physical activity of more than four hours per week or regular hard training or competitive sports several times per week).

During the follow-up period, 1,664 participants developed an MI, of which 58.8 percent were men and 41.2 percent were women. The mean age at MI was 70.9 years old and the median time from baseline to MI was 14.6 years.

The researchers found that 54 percent of the participants who developed an MI practice light leisure time physical activity, while more men than women reported moderate or high leisure time physical activity.

People who were more physically active were more likely to have a higher socioeconomic status and better lung function and less likely to smoke, drink alcohol or have hypertension. However, the researchers noted there were no differences between leisure time physical activity groups with regards to diabetes, body mass index, systolic blood pressure and cholesterol.

In addition, 25.5 percent of the MIs were fatal immediately after MI onset. The odds ratios of fatal versus non-fatal MI were 0.68 for light physical activity and 0.53 for moderate/high physical activity.

During a mean follow-up period of 5.6 years, 29.1 percent of MI survivors developed heart failure for an incidence rate of 48.9 per 1,000 person-years. The researchers mentioned there was no statistically significant difference between leisure time physical activity and the risk of heart failure.

Meanwhile, during a mean follow-up period of 6.9 years, 83.4 percent of MI survivors died for a mortality rate of 121 per 1,000 person-years. The mortality rates were similar for all levels of leisure time physical activity. After multivariable adjustment, the hazard ratios were 0.89 for light leisure time physical activity and 0.90 for moderate/high leisure time physical activity.

“This was an observational study so we cannot conclude that the associations are causal,” Prescott said in a news release. “The results need to be confirmed before we can make strong recommendations. But I think it’s safe to say that we already knew exercise was good for health and this might indicate that continuing to exercise even after developing atherosclerosis may reduce the seriousness of a heart attack if it does occur.”

The study had a few limitations, according to the researchers, including that participants self-reported their leisure time physical activity. They also did not have information of the size of infarction and of left ventricular ejection at the time of MI and the time elapsed between baseline data and the date of MI.

“This study shows that higher levels of [leisure time physical activity] prior to MI were associated with a lower risk of fatal MI, but did not affect the risk of subsequently developing heart failure and death after MI,” the researchers wrote. “The findings may prove important for future recommendations on [leisure time physical activity], but need to be confirmed in larger prospective studies.”