A daily baby aspirin is often recommended by doctors to help prevent heart attacks or stroke, but for people over 70 years old the benefits may be offset by bleeding risks, investigators report. "The balance of harm and benefit could tip either way," they say.

Elderly individuals are at increased risk of having adverse reactions to drugs, Dr. Mark R. Nelson, from the University of Tasmania in Hobart, Australia, and colleagues note in the Online First edition of the British Medical Journal. However, most of the clinical trials looking into the prevention of cardiovascular events with aspirin have involved middle-aged subjects.

To further investigate the matter, the research team constructed a mathematical model based on clinical trial data and demographics to compare risks and benefits of low-dose aspirin in a theoretical cohort of 10,000 men and 10,000 women ages 70 to 74. The virtual participants were "followed" until they died or reached 100 years of age.

The model suggested that, for men, routine low-dose aspirin therapy would prevent 389 heart attacks and 19 strokes; for women, the numbers were 321 heart attacks and 35 strokes.

However, this benefit was offset by an extra 499 episodes of gastric bleeding in men and 572 in women. On top of that, the team calculated that 76 more men and 54 more women would suffer bleeding in the brain.

"On balance, there was no indication of a net benefit or harm in terms of deaths, years of life saved, or years of healthy life saved," the researchers report.

Their findings highlight the need for a randomized clinical trial of aspirin use in elderly patients, they add, and "underscore the importance of targeting preventive treatment to those for whom the potential balance of benefit versus harm is optimal."

SOURCE: BMJ Online First, May 19, 2005.