It's the first finding of its kind. More studies are needed to check the results before recommendations can be made.
The study was done in Spain. The researchers included Ramón Hermida, PhD, of the University of Vigo. Their report appears in the Journal of the American College of Cardiology.
Hermida's study included 328 people with mild, untreated stage 1 high blood pressure. Stage 1 high blood pressure is defined as a systolic reading (top number) of 140-159 and a diastolic reading (bottom number) of 90-99.
The patients were about 44 years old, on average.
All of the patients got advice on lowering their blood pressure without medicine (including dietary recommendations for high blood pressure). They were split into three groups.
One group wasn't given any aspirin (169 people). A second group took 100 milligrams of aspirin every morning (77 people). A third group took the same dose of aspirin at night (82 people).
All patients wore devices that monitored their blood pressure around the clock. Blood pressure readings were automatically recorded every 20 minutes during the day and every half hour at night.
After three months, these were the results:
- Aspirin at night: Significant drop in blood pressure
- Aspirin in the morning: Slightly higher blood pressure
- No aspirin: Slightly lower blood pressure
The biggest blood pressure change was in the patients who took aspirin at night, the study shows.
How much did their blood pressure drop?
- Systolic blood pressure (the top number): down 6.8
- Diastolic blood pressure (the bottom number): down 1.6
In people older than 50 a systolic blood pressure greater than 140 is a much more important risk factor for heart disease than the diastolic blood pressure reading.
Nearly nine out of 10 who took aspirin at night had a drop in blood pressure, the study shows.
The reasons for the time trends aren't clear, according to the researchers. The topic deserves further study, they write.
The results are "surprising and thought provoking" and the potential implications for blood pressure treatment are "most important," writes Franz Messerli, MD, FACC, in a journal editorial.
Messerli, who works at St. Luke's Roosevelt Hospital Center in New York, writes that he "wholeheartedly agrees" that more studies are needed.
But he's not totally sold on the idea that taking aspirin at night eases high blood pressure.
"As provocative as these findings are, they originate from a single source only," he writes, calling for "extreme caution" in interpreting the results.
Improving Blood Pressure
While scientists tackle the aspirin-at-night topic, there are steps you can take right now to handle high blood pressure.
Nearly one in three U.S. adults has high blood pressure, and almost a third of them don't know it, according to the American Heart Association (AHA).
10 Steps to Better Blood Pressure
The AHA offers these tips for better blood pressure:
- Get your blood pressure checked. Knowledge is a powerful first step. High blood pressure doesn't make you feel ill; it's called the silent killer.
- Get medical advice. Your doctor can help determine what strategies will help most with any blood pressure issues.
Smoking raises your odds of heart problems, stroke, and other health problems. Quitting can take several tries, so hang in there and get support.
Become more active. If you've been idle, check in with your doctor first.
Eat healthfully. Cutting down on salt can help. Make fruits, vegetables, and low- or no-fat dairy products part of a healthy diet.
Take medications, if needed. Work with your doctor to see if you need blood pressure drugs.
Lose excess weight. Your blood pressure may improve as you shed extra pounds.
Don't drink too much alcohol. The AHA suggests limiting alcohol to no more than one or two drinks per day.
Manage your stress. You'll be helping your heart and blood vessels take it easy.
- Talk to your doctor about your medications. Some medications can affect blood pressure