Sedentary Individuals at Increased Risk of Fatal Myocardial Infarction

Kim Wadt Hansen, MD, PhD

Patients who exercise less are more likely to suffer a fatal heart attack, according to a new study from investigators in Europe.

A pooled analysis of data from 10 cohort studies examining myocardial infarction, results of the study indicate patients with lower levels of physical activity were at an increased risk of death during the acute phase of a myocardial infarction.

"Almost 18% of patients with a heart attack died within 28 days, substantiating the severity of this condition. We found an immediate survival benefit of prior physical activity in the setting of a heart attack, a benefit which seemed preserved at 28 days,” said Kim Wadt Hansen, MD, PhD, lead investigator and postdoctoral research fellow from the Department of Cardiology at Bispebjerg Hospital in Denmark, in a statement.

With an interest in further assessment of the cardioprotective effects of physical activity, investigators sought to explore how physical activity levels might influence risk of death following myocardial infarction. To do so, investigators designed their study as a collaborative pooled analysis of European observational cohorts including patients with a baseline assessment of physical activity, conventional risk factors, and follow-up on myocardial infarction and death.

In total, investigators invited 17 cohort studies to contribute data for analysis. After exclusion of nonrespondents and those with insufficient data, 10 studies were identified for inclusion in the pooled analysis. These 10 studies were conducted across a multitude of European nations, including Denmark, the Netherlands, Greece, and the United Kingdom, and contained data related to 1,495,254 individuals. Among this patient population, 28,140 individuals developed an incident myocardial infarction during follow-up and these individuals were included in the investigators’ final analysis.

For the purpose of analysis, investigators created 4 groups to classify levels of physical activity among participants—sedentary, low, moderate, and high. The criteria for placement into these groups were defined as less than 7 metabolic equivalents (MET)-hours per week, 7-16 MET-hours per week, 16.1-32 MET-hours per week, and more than 32 MET-hours per week, respectively.

Of the 28,140 patients included in the final analyses, 4976 (17.7%) died within 28 days of their incident myocardial infarction. Upon analysis, results indicated 62.3% (n=3101) of these events were classified as an instant fatal myocardial infarction.

In comparison to sedentary individuals, those reporting higher levels of physical activity had lower adjusted odds of instant fatal myocardial infraction, with decreased odds for those with low (OR, 0.79; 95% CI, 0.60-1.04), moderate (OR, 0.67; 95% CI, 0.51-0.89), and high (OR, 0.55; 95% CI, 0.40-0.76) physical activity levels. Additionally, similar results were observed when assessing for 28-day fatal myocardial infarction, with decreased odds for low (OR, 0.85; 95% CI, 0.71-1.03), moderate (OR, 0.64; 95% CI 0.51-0.80), and high (OR, 0.72; 95% CI, 0.51-1.00) physical activity levels.

Investigators noted a low-to-moderate degree of heterogeneity was observed in the analysis of instant fatal myocardial infarction (I²=47.3%) but not in the analysis of 28-day fatal myocardial infarction (I²=0.0%). Investigators also cautioned against over-interpretation of results based on multiple limitations within their study, which included the observational nature of design and potential bias in misclassification of events, among others.

"Based on our analyses, even a low amount of leisure-time physical activity may in fact be beneficial against fatal heart attacks, but statistical uncertainty precludes us from drawing any firm conclusions on that point,” added Hansen.

This study, “Association of fatal myocardial infarction with past level of physical activity: a pooled analysis of cohort studies,” was published in the European Journal of Preventive Cardiology.