New Bedtime Ritual for Hypertensive: Aspirin

Lowers pressure when taken in evening, not in morning

FRIDAY, May 17, 2002 (HealthDayNews) -- A daily baby aspirin pill, often recommended to lower the risks of heart disease, can also reduce high blood pressure -- but only if it's taken at bedtime.

In a new study of 109 men and women who suffered from mild hypertension, which is a blood pressure reading of no higher than 160/100 mm Hg, those who took a 100-milligram tablet of aspirin before going to bed had a significant reduction in their blood pressure over a three-month period. Those who took the aspirin in the morning had no reduction at all.

"If you're going to recommend a daily aspirin for protection against heart disease, you will not do any worse and will probably do better to take it in the evening because you will also be lowering your blood pressure," says study author Ramon C. Hermida, director of bioengineering and chronobiology at the University of Vigo in Spain.

He presented the results of the study, which is ongoing in conjunction with the University Clinical Hospital in Santiago, Spain, today at the annual scientific meeting of the American Society of Hypertension in New York City.

The study participants, who had all received diagnoses for mild hypertension, were taking no other medication, although they were all being advised to reduce caloric and sodium intake, to exercise and to eliminate smoking and drinking.

Researchers monitored the participants' blood pressure levels every half hour for 48 hours before they began the aspirin therapy and repeated the two-day intensive monitoring for 48 hours after three months of aspirin therapy.

Those who had taken aspirin before they went to bed, on the average of 11 p.m., decreased their systolic blood pressure (the upper figure) by an average of 5.5 mm and their diastolic blood pressure (the lower one) by an average of 4 mm over the three-month duration of the study. Those who took a morning aspirin, usually at about 8 a.m., saw no reduction of blood pressure at all.

"This is very, very clinically relevant," Hermida says, because it means that those with mild hypertension could avoid taking any medication to reduce their blood pressure.

Blood pressure measures the rate at which blood pushes against the walls of the arteries as it moves through the body. The systolic pressure is when your heart is contracted and is pumping the blood out into the body, and the diastolic pressure is the rate is when the heart is resting between pumps. When blood pressure is too high on a regular basis, it can damage the arteries, which in turn increases your risk for a variety of diseases such as atherosclerosis and heart disease.

"This is a very significant finding. This is the first well-conducted study that looks at the timing of aspirin intake on blood pressure lowering in people who have hypertension," says Michael Smolensky, a professor at the University of Texas School of Public Health and co-author of the book The Body Clock Guide to Better Health.

"It shows how significant the body's circadian rhythms are that the overall effect of aspirin on blood pressure depends entirely on the time the pill is taken," he says.

Smolensky says that while a daily aspirin is increasingly recommended for people at high risk for heart disease, there is usually no time-specific recommendation for when the pill should be taken. Given that high blood pressure is a risk factor for heart disease, people would do well to take their aspirin in the evening.

In addition, he says, studies have shown chronic aspirin intake is better tolerated by the body when given at night, lessening stomach upset and other side effects.

Hermida says that while no one is sure exactly why the aspirin has an impact in the evening and none in that the morning, he says it could be that aspirin slows down the production of hormones and other substances in the body that cause clotting. Many of those are produced while the body is at rest.

Both doctors say that before starting to take an aspirin at night, you should check with your doctor, particularly if you are already taking medication for high blood pressure.

"If you shift your aspirin-taking to bedtime, you could lower your blood pressure too much, which means when you get up in the middle of the night to use the bathroom you could faint," Smolensky says.

"Patients should also be cautioned that doctors might be unaware of the timing effects of aspirin," he says. "This is new."

What To Do: For basic information about blood pressure you can visit Lifeclinic. Read more about aspirin's heart-healthy effects from the American Heart Association.

SOURCES: Ramon C. Hermida, Ph.D., director, bioengineering and chronobiology labs, University of Vigo, and clinical researcher, University Clinical Hospital, Santiago, Spain; Michael Smolensky, Ph.D., professor, University of Texas School of Public Health, Houston; May 17, 2002, presentation, American Society of Hypertension annual scientific meeting, New York City
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