May 15, 2002 -- Taking aspirin at the right time may be the key to preventing heart attacks, stroke, and even high blood pressure. The common yet potent drug works best at bedtime, a Spanish study shows.
Ramon C. Hermida, PhD, of the University of Vigo, Spain, reported the findings at this week's annual meeting of the American Society of Hypertension.
"Timed administration of low-dose aspirin could be a valuable approach not only for the prevention of major cardiovascular events, but also for the control of blood pressure in patients with mild-to-moderate [high blood pressure]," Hermida says in a press release.
Low-dose aspirin is known to reduce the risk of heart attack in high-risk patients. It also seems to help lower high blood pressure, but studies looking at this effect yield confusing results. Now there may be an explanation: aspirin only lowers blood pressure when taken at bedtime.
Hermida's team studied 109 men and women with mild high blood pressure. All of them went on a diet-and-exercise regimen. They were randomly assigned to three groups. One group didn't take any aspirin. A second group took a low-dose aspirin every morning when they got up. The third group took a low-dose aspirin every night when they went to bed.
Aspirin didn't affect blood pressure if given in the morning. But when given at night, it had a significant effect: a 7.0 mmHg decrease in systolic blood pressure (the top number in a blood-pressure reading) and a 4.8 mmHg decrease in diastolic blood pressure (the bottom number).
Hermida suggests that the body might absorb aspirin more quickly in the morning than at night. He advises researchers to look at when aspirin is given in future studies.
While the study results are interesting, they don't change U.S. recommendations. As set forth by the U.S. Preventive Services Task Force, people whose risk of heart attack is 5% over five years (or 10% over 10 years) should take one baby aspirin every day. Those whose five-year risk of a heart attack is 3% probably also would benefit.
The reason for caution is that aspirin -- even a baby aspirin -- definitely increases the risk of bleeding in the stomach and gut. It may also increase the risk of a hemorrhagic stroke. David Atkins, MD, is director of the U.S. Preventive Services Task Force.
"In terms of preventing heart attack, low-dose aspirin is effective, but whether it is safer than high-dose aspirin we don't know," Atkins tells WebMD. "While it is just as effective, it looks just as risky."