For decades, a daily low-dose aspirin was a default suggestion for anyone worried about a heart attack. The thinking was straightforward. Aspirin thins the blood, blood clots cause heart attacks and strokes, so a small daily dose should keep the plumbing clear. Many of my patients still ask if they should start one, often because a parent or neighbor takes it.
The picture is more nuanced than that, and the guidelines have shifted. The most important distinction is the difference between primary prevention and secondary prevention. They sound similar but the math behind them is very different.
Primary vs Secondary Prevention
Primary prevention means using aspirin to prevent a first heart attack or stroke in someone who has not had one. The person feels healthy. We are trying to head off something that has not happened yet.
Secondary prevention means using aspirin in someone who already has cardiovascular disease. This includes people who have had a heart attack, a stroke or transient ischemic attack (TIA, sometimes called a mini-stroke), or peripheral artery disease (PAD). The disease is established. We are trying to keep a second event from happening.
That distinction drives the recommendation.
What the Guidelines Now Say About Primary Prevention
In 2022, the U.S. Preventive Services Task Force updated its recommendation on aspirin for primary prevention, and the change was significant. The full document is here: USPSTF Aspirin Recommendation.
The short version:
- For adults aged 40 to 59 with a 10 percent or higher 10 year cardiovascular risk, starting low dose aspirin offers only a small net benefit. The decision should be individual, made together with your physician.
- For adults 60 and older who have not had cardiovascular disease, the Task Force now recommends against starting aspirin for primary prevention.
The NICE guidance in the United Kingdom takes a similar cautious stance. The clinical knowledge summary cited at NCBI notes that aspirin is not recommended for routine primary prevention, and any consideration should be a careful discussion of risks and benefits with the individual patient.
Why the change? The benefit of aspirin in healthy people is real but small. The risk of serious bleeding, especially in the gut and the brain, rises with age. Somewhere in your sixties, for most people, the bleeding risk starts to outweigh the heart protective benefit. That tipping point is what the new guidance reflects.
Secondary Prevention Is a Different Conversation
If you have had a heart attack, a stroke or TIA, or have been diagnosed with PAD, the math flips. Your risk of a second event is much higher than the average person’s risk of a first one. Aspirin’s benefit in that setting is substantial and well established.
For these patients, low dose aspirin is typically part of long term care unless there is a specific reason not to take it. Examples of reasons we might pause include active bleeding, certain ulcer conditions, severe allergies to aspirin, or a planned procedure where bleeding risk has to be managed.
The takeaway: if you already have cardiovascular disease, aspirin is usually doing real work for you. Do not stop it on your own without checking with your physician.
What Changed Our Thinking on Bleeding
A few things converged. Newer studies in healthy adults (most notably the ASPREE trial in older adults and the ARRIVE and ASCEND trials in middle aged adults) showed that the absolute risk reduction for heart attack and stroke was smaller than older data suggested, while bleeding events were more common than we used to assume.
At the same time, we have gotten better at the rest of cardiovascular prevention: statins, blood pressure control, smoking cessation, and treatments for diabetes. Aspirin used to be one of the few tools we had. Now it sits among several, and we can be choosier about who it actually helps.
So What Should You Do?
- If you are currently taking aspirin because someone told you years ago to “just take a baby aspirin,” bring it up at your next visit. We will look at your age, your cardiovascular risk score, your bleeding risk, and any other medications you take.
- If you have been told to take aspirin because of a prior heart attack, stroke, TIA, or PAD, keep taking it as prescribed. Do not stop on your own.
- If you are weighing whether to start, do not decide based on what worked for a relative or a friend. Their risk profile is not yours.
- Mention every over the counter medication and supplement you take, including fish oil and NSAIDs like ibuprofen. They affect bleeding risk too.
The right answer about aspirin used to feel obvious. It is now a personalized decision, and that is actually good news. We have more information than ever about who genuinely benefits.
Sources
- U.S. Preventive Services Task Force: Aspirin Use to Prevent Cardiovascular Disease
- NICE Clinical Knowledge Summary on Cardiovascular Risk Assessment and Lipid Modification
As always, nothing here replaces a conversation with your own physician. If you have questions about whether aspirin makes sense for you, bring them to your next visit.
