Aspirin More Beneficial if Taken at Night

People who take aspirin to keep their blood pressure down will get more benefit if they take it at bedtime, researchers say.

The hormones and other chemicals the aspirin acts on are most active at night, they say.

Though blood pressure tends to drop at night, that is the time when the body is setting everything in motion for the pressure to go up the next day, during waking hours, said Ramón C. Hermida of the University of Vigo in Spain.

“If you take the aspirin in the morning, it is not going to be effective because aspirin basically has an effect for fours hours or so,” Dr. Hermida said.

While doctors often advise patients to take aspirin to help control their blood pressure, he said, they generally do not give any advice about the time of the day.

For the study, presented at a conference of the American Society of Hypertension, researchers looked at more than 240 people with a condition known as prehypertension over three months. Some took aspirin in the morning, others at night and some not at all. Their blood pressure was taken regularly during the study, and the researchers also kept track of physical activity.