For most people with high blood pressure, aspirin is not automatically recommended. Current guidelines say aspirin for primary prevention (meaning you haven’t had a heart attack or stroke yet) should only be considered in adults aged 40 to 59 whose 10-year cardiovascular risk is 10% or higher, and only after blood pressure is well controlled. If you’re 60 or older, the U.S. Preventive Services Task Force now recommends against starting aspirin for primary prevention entirely.
The picture changes if you’ve already had a heart attack or stroke. In that case, aspirin is a standard part of treatment regardless of age. But for people with hypertension alone, the decision is more nuanced than it used to be.
Blood Pressure Must Be Controlled First
This is the most important prerequisite. Starting aspirin while blood pressure is still elevated raises the risk of hemorrhagic stroke, a type of stroke caused by bleeding in the brain. Guidelines consistently state that low-dose aspirin should only be considered once blood pressure is controlled.
What counts as “controlled” has been studied in some detail. The Hypertension Optimal Treatment (HOT) trial found clear benefits from aspirin in patients whose diastolic blood pressure (the bottom number) was below 85 mm Hg, but not in those whose readings remained high. A separate analysis found no benefit from aspirin in patients with a systolic reading (the top number) above 145 mm Hg. Patients whose systolic pressure fell between 130 and 145 mm Hg saw a 25% reduction in heart attacks. In practical terms, if your blood pressure is still running high and you haven’t yet gotten it into a well-managed range with lifestyle changes or medication, aspirin is not the right next step.
The Age and Risk Thresholds
The 2022 USPSTF recommendation breaks the decision down by age:
- Ages 40 to 59: Aspirin can be considered if your estimated 10-year cardiovascular disease risk is 10% or greater, you’re not at increased risk for bleeding, and you’re willing to take it daily. The task force rates this a Grade C recommendation, meaning the net benefit is real but small.
- Age 60 and older: Do not start aspirin for primary prevention. This is a Grade D recommendation, meaning the bleeding risks outweigh the cardiovascular benefits for this age group.
Your 10-year cardiovascular risk is estimated using the ASCVD risk calculator, which factors in your age, sex, race, blood pressure, cholesterol levels, diabetes status, and smoking history. Your doctor can run this calculation during a routine visit, or you can find the calculator through the American College of Cardiology’s website. The 10% threshold is the point at which the potential heart-protective benefit of aspirin begins to outweigh the bleeding risk, at least in the 40 to 59 age range.
Why Guidelines Have Become More Cautious
Aspirin prevents blood clots by making platelets less sticky. That’s valuable for preventing heart attacks and certain strokes, but the same mechanism increases the risk of bleeding, particularly in the stomach and intestines. In older adults, the bleeding risk climbs while the relative cardiovascular benefit shrinks, which is why the recommendation shifted against routine aspirin use after 60.
Even in the 40 to 59 group, the USPSTF describes the net benefit as “small.” That’s a meaningful word. It means aspirin isn’t a clear win for everyone in that range. It means you and your doctor should weigh your specific risk factors: Do you have a history of ulcers or gastrointestinal bleeding? Are you taking other medications that thin the blood or irritate the stomach lining? These factors can tip the balance against aspirin even if your cardiovascular risk score qualifies you.
The Exception: Chronic Kidney Disease
One group of hypertensive patients appears to benefit more dramatically from aspirin. The HOT trial found that patients with reduced kidney function (specifically, a filtration rate below 45 ml/min) experienced a 66% reduction in major cardiovascular events on aspirin, compared with only a 9% reduction in those with normal kidney function. Among every 1,000 patients with significantly reduced kidney function treated for about four years, aspirin prevented 76 major cardiovascular events and 54 deaths, while causing 27 additional major bleeding episodes.
That’s a ratio where the benefits substantially outweigh the harms, unlike the more balanced equation in the general hypertensive population. If you have both high blood pressure and known kidney disease, this is a conversation worth having with your doctor sooner rather than later.
If You’ve Already Had a Heart Attack or Stroke
Everything above applies to primary prevention, meaning you’re trying to avoid a first cardiovascular event. If you’ve already had a heart attack, stroke, or been diagnosed with atherosclerotic cardiovascular disease, aspirin is part of standard secondary prevention treatment. Guidelines from the European Society of Cardiology recommend 81 to 100 mg daily in this context, while the American Diabetes Association recommends 75 to 162 mg daily for patients with both diabetes and established cardiovascular disease. The typical dose in the U.S. is 81 mg, the standard low-dose tablet.
What the Decision Looks Like in Practice
If you have high blood pressure and are wondering whether aspirin belongs in your routine, the sequence matters. First, get your blood pressure into a controlled range, ideally with diastolic readings below 85 mm Hg and systolic readings well under 145. Then, if you’re between 40 and 59, have your cardiovascular risk formally calculated. If that risk is 10% or higher and you don’t have a history of bleeding problems, aspirin becomes a reasonable option to discuss.
If you’re 60 or older with no history of heart attack or stroke, the current evidence says the risks of starting aspirin outweigh the benefits. And if you’re already taking aspirin that was prescribed years ago under older, more permissive guidelines, it’s worth revisiting whether that prescription still makes sense given what we now know.