Contact:  Kristin Fayer  [Searle]   (847) 470-6728 or Maura McLaughlin   [Beth Israel Deaconess Medical Center]   (617) 667-7297


Research Highlights Public Health Problem

MARCH 18, 1997 — Anaheim, CA — The likelihood of having a heart attack (acute myocardial infarction) is 40 percent higher between 6 a.m. and noon than during the rest of the day, according to new data presented today at the American College of Cardiology's 46th Annual Session. Similarly, the risk for sudden cardiac death is 29 percent higher during these morning hours. According to this research, a meta-analysis which looked at 48 studies involving more than 73,000 patients worldwide, heart attacks occurring in the morning account for nine percent of total acute myocardial infarctions and nearly seven percent of sudden cardiac deaths. Approximately one of every 11 acute myocardial infarctions and one of every 15 sudden cardiac deaths are attributable to this morning excess.

"While we have known about this morning excess of cardiovascular events for some time, we now have the data to quantify that risk," commented Murray A. Mittleman, MD, DrPH, Beth Israel Deaconess Medical Center and Harvard Medical School, and one of the study's authors. "These data suggest that if we could eliminate this morning peak, approximately 135,000 heart attacks and 17,000 deaths potentially could be averted each year in the United States. Further study is required to determine the reduction in costs and disease burden in this population."

This meta-analysis summarized published reports of circadian variation of myocardial infarction and sudden cardiac death. The authors pooled a decade's worth of data (from January 1, 1985 to June 30, 1996) with 73,414 patient records to define the proportion of events that are attributable to the morning excess and evaluate the potential impact of the elimination of the morning peak of cardiovascular events.

There are 1.5 million heart attacks annually, and heart attack is the single leading cause of death in America, accounting for nearly 500,000 fatalities each year. Sudden cardiac death is the sudden, abrupt loss of heart function in a person who may or may not have diagnosed heart disease, and is responsible for 250,000 deaths annually.

Day-night patterns in blood pressure, angina, myocardial infarction, sudden cardiac death and stroke have been well-described, and clearly support a circadian variation in cardiovascular disease. This time period between 6 a.m. and noon represents a particularly vulnerable time for patients with ischemic heart disease.

The morning is the time when the body's clotting system is more active, blood pressure surges and heart rate increases. In addition, the level and activity of stress hormones (e.g., catecholamines) that can induce blood vessels to constrict increases in the morning. There also may be reduced blood flow to the heart. Combined with these mechanisms are the increased mental and physical stresses that typically occur after waking.

"Potentially, the incidence of morning cardiovascular events may be reduced by introducing preventive measures, including medications, that are designed to be efficacious in the morning hours," said Dr. Mittleman. "Such treatment strategies have the theoretical advantage of offering maximum protection when the cardiovascular event rate is highest and patients are most vulnerable."

Research in Cardiovascular Health

Long-term prospective trials, such as CONVINCE and ALLHAT, evaluating several pharmacologic strategies for the primary prevention of myocardial infarction and death are currently underway, and are expected to yield final results in the next five years. "These trials will provide information that will help us optimize our approach to the treatment of hypertension, an important risk factor for the occurrence of cardiovascular disease," commented Dr. Mittleman.

Beth Israel Deaconess Medical Center is a major teaching affiliate of Harvard Medical School and a founding member of CAREGROUPSM, an organized system of quality healthcare serving the individual, family and community.

# # #

Return to the press releases page.

©1996 Searle. Send questions or comments to or bug reports to