WEDNESDAY, May 14 (HealthDay News) -- A daily aspirin can
control prehypertension, but only if it is taken at bedtime, a
Spanish study shows.
An aspirin taken every morning didn't lower the blood pressure
of prehypertensive people, but the evening regimen did, Dr. Ramon
C. Hermida reported Wednesday at the American Society of
Hypertension annual meeting, in New Orleans.
A previous study by Hermida, who is director of bioengineering
and chronobiology at the University of Vigo, showed the same
beneficial effect of bedtime aspirin for people with moderately
high blood pressure. The new report is the first study to show the
drug's benefit -- although only when taken at night -- with
prehypertension, defined as blood pressure just below the 140/90
level. Prehypertension is a known warning sign of future risk of
heart disease, stroke and other cardiovascular problems.
Why aspirin should do its good work for blood pressure at night
but not in the daytime is not clear, Hermida said. Research
indicates that it can slow the production of hormones and other
substances in the body that cause clotting, many of which are
produced while the body is at rest.
The three-month study included 244 adults diagnosed with
prehypertension. A third of them were advised to follow general
rules of hygiene and diet designed to reduce blood pressure,
another third were told to take a 100-milligram aspirin tablet
every night at bedtime, and the final third were told to take the
same aspirin dose on awakening.
Researchers monitored blood pressure levels at 20-minute
intervals from 7 a.m. to 11 p.m. and at 30-minute intervals at
night before the trial began and three months later.
Systolic blood pressure (the higher number in the 140/90
reading) dropped 5.4 points and diastolic pressure by 3.4 points
for those taking aspirin before bedtime. No drop in blood pressure
was found in those taking morning aspirin or following the general
guidelines.
"There is some evidence that taking a variety of medications,
including those for hypertension, at night is associated with
greater blood pressure reduction than taking them in the morning,"
said Dr. Suzanne Oparil, president of the American Society for
Hypertension. "I don't think we know why."
It's possible that there might be better absorption of the
medication by the gastrointestinal tract at night, said Oparil, who
is a professor of medicine at the University of Alabama at
Birmingham.
"It's all a little bit speculative about why, but I think the
observation is solid," she said.
In a statement, Hermida said the new findings "show us that we
cannot underestimate the impact of the body's circadian
rhythms."
"The beneficial effects of time-dependent administration of
aspirin have until now been largely unknown in people with
prehypertension," he said. "Personalizing treatment according to
one's own rhythms gives us a new option to optimize blood pressure
control and reduce the risk of cardiovascular disease down the
line."
More information
Aspirin in all its aspects is described by the
U.S. National Library of Medicine.
