FAU.edu – A leading medical journal has published a meta-analysis of six large-scale randomized clinical trials of aspirin in the primary prevention of cardiovascular disease among over 95,000 apparently healthy men and women worldwide. Charles H. Hennekens, M.D., a professor in the College of Biomedical Science at Florida Atlantic University, is a member of an international writing group that co-authored the meta-analysis in the May 30, 2009 issue of The Lancet.

Hennekens was the founding principal investigator of the two trials from the United States, funded by the National Institutes of Health. The Physician’s Health Study was the first to demonstrate that aspirin prevents a first heart attack. The Women’s Health Study was the first to demonstrate that aspirin prevents a first stroke. Two of the trials are from the United Kingdom (U.K.), and the final two trials are from Italy and Sweden.

The apparently healthy people in this meta-analysis were at very low risk of a first coronary event (less than five percent over 10 years). The individuals assigned to aspirin had significant, relative reductions in risks of all obstructions in the arteries due mainly to a 23 percent lower risk of a first heart attack. In contrast, in this low risk population, the absolute number of events due to obstructions in the arteries prevented by aspirin is about equal to the absolute increase in major bleeds (mainly gastrointestinal). Several ongoing trials will provide the necessary information on absolute benefits and risks of aspirin in people at moderate and high risks of a first heart attack or stroke, as well as a rational basis for clinical guidelines.

“Nobody would disagree that all patients who have survived a prior heart attack or stroke and have a 10-year risk of a recurrent coronary event of more than 20 percent should be given aspirin,” said Hennekens. “The absolute benefits on occlusion (obstructions in the artery) are large in comparison to the absolute risks of major bleeding. The major disadvantage of waiting to prescribe aspirin until after there is clinical evidence of occlusion is that, for many, the initial event is death or long-term disability.”

Furthermore, in the U.S. today, 40 percent of men and women over age 40 have metabolic syndrome, a constellation of obesity, abnormal lipids, high blood pressure and insulin resistance, a precursor of diabetes. Patients with metabolic syndrome have a 10-year risk of a first heart attack of 16-18 percent.

The U.S. Preventive Services Task Force has recently updated their guidelines for aspirin in the primary prevention of cardiovascular disease. Hennekens believes that at present, a prudent course of action for healthcare providers is to make individual clinical judgments about the use of aspirin for those apparently healthy men and women whose absolute risks of occlusion will outweigh their risks of major bleeding.