Cardiology Topic

Start the aspirin?

Six patients with no prior heart attack or stroke. Since ASCEND, ARRIVE and ASPREE, aspirin for primary prevention is a narrow, individual decision, and bleeding risk decides most of it.

Reviewed October 2026 · verify against current guidelines

Aspirin · 1 of 9

Start the aspirin?

Primary prevention: no prior heart attack or stroke. Make your call on each — give or don't — before reading on. The answers are at the end.

Your call

52, 10-year CVD risk 12%, no bleeding risk
74, healthy, asks to start a daily aspirin
58, type 2 diabetes, smoker, LDL 160
64, moderate risk, peptic ulcer 3 years ago
79, on aspirin for 15 years, never had CVD
48, low risk, takes ibuprofen most days

Aspirin · 2 of 9

One pill, two effects.

Aspirin permanently blocks COX-1 in platelets. The same block that prevents clots also causes bleeding, so every benefit is paid for in bleeding risk.

Where it acts

Arachidonic acid → COX-1 (blocked by aspirin) → platelet thromboxane A2 (aggregation → arterial clot) and gastric prostaglandins (protect the stomach lining).

The benefit	The cost
Fewer nonfatal heart attacks, mainly	More GI and intracranial bleeding
Small absolute effect when baseline risk is low	Bleeding risk rises with age, as CVD risk does

Pharmacology

Duration	Platelets lack a nucleus, so the block lasts their 7 to 10 day lifespan
Dose	Most guidelines use 75 to 100 mg a day (ADA allows up to 162 mg); ASCEND, ARRIVE and ASPREE all used 100 mg

Why primary prevention is different — after a heart attack or stroke, event risk is high, and the clots prevented far outnumber the bleeds caused. Before any event, risk is lower, so the two numbers move closer together.

Not about secondary prevention — after MI, stroke or a stent, aspirin stays. This series is about people with none of these.

Aspirin · 3 of 9

2018: three trials, one year.

Three large placebo-controlled trials, published within weeks of each other. In each, extra bleeds matched or outnumbered the events prevented.

Per 1,000 people treated, over each trial

Trial	Population	Events prevented	Bleeds caused
ASCEND	15,480, diabetes	11	9
ARRIVE	12,546, moderate risk	2 (not significant)	5 (GI)
ASPREE	19,114, age ≥70	~3 (not significant)	~11

ASPREE estimated from published rates per 1,000 person-years over a median 4.7 years.

ASCEND	Serious vascular events 8.5% vs 9.6% (RR 0.88). Major bleeding 4.1% vs 3.2% (RR 1.29)
ARRIVE	Primary outcome 4.29% vs 4.48% (HR 0.96). GI bleeding 0.97% vs 0.46%, about twofold and mostly mild
ASPREE	Disability-free survival unchanged (HR 1.01). Major hemorrhage 3.8% vs 2.8% (HR 1.38)

Why the benefit stayed small — lower risk than planned: ARRIVE enrolled for moderate risk, but its event rates were lower than expected. And the pooled effect was small: ATT 2009 found serious vascular events of 0.51% vs 0.57% a year.

Aspirin · 4 of 9

Over 70: no gain, more bleeding.

ASPREE gave 100 mg a day to healthy older adults. It did not extend healthy life, and bleeding rose.

Disability-free survival	Major hemorrhage
HR 1.01 — no difference in the primary outcome at a median 4.7 years. CVD events also unchanged	3.8% vs 2.8% — HR 1.38. Mostly GI and intracranial bleeding

The unexpected finding

All-cause death 5.9% vs 5.2% (HR 1.14), driven by more cancer deaths (HR 1.31). Cancer was the cause in about half of all deaths.

What the guidelines say

USPSTF 2022	Recommends against starting aspirin for primary prevention at 60 or older (grade D)
ACC/AHA 2019	Should not be given routinely over 70 (class III, harm)

Why the cancer signal is debated — the investigators urged caution: older trials had suggested aspirin lowers cancer death over the long term. And diagnoses did not differ: cancer deaths rose, but new cancers did not differ significantly between groups.

Who was enrolled — 19,114 people aged 70 or older (65 for Black and Hispanic US participants), free of CVD, dementia and disability.

Aspirin · 5 of 9

Who might still benefit.

No guideline recommends routine aspirin for primary prevention. Each leaves room for an individual decision in younger, higher-risk adults with low bleeding risk.

Guidelines side by side

	USPSTF 2022	ACC/AHA 2019	ADA 2026	ESC 2021
Who	Age 40 to 59, 10-year CVD risk ≥10%	Age 40 to 70 at higher ASCVD risk	Diabetes at increased CV risk	High CV risk, including diabetes; not low-to-moderate risk
Wording	An individual decision; net benefit is small	Might be considered	May be considered after discussion	May be considered
Grade	C	IIb	A	IIb
Dose	Low dose, 81 mg	75 to 100 mg	75 to 162 mg	75 to 100 mg

Common ground

Increased bleeding risk weighs against aspirin in all four
With established ASCVD, aspirin is still recommended; this is secondary prevention
Risk scores changed in 2026. The 2026 ACC/AHA dyslipidemia guideline replaced the Pooled Cohort Equations with PREVENT, which gives lower estimates for the same patient. Aspirin thresholds were set with the older scores.

The coronary calcium argument — for it: in cohort studies, a CAC score of 100 or more marks people whose event risk may outweigh bleeding. Against it: no completed randomized trial has tested CAC-guided aspirin. USPSTF has not endorsed it.

Aspirin · 6 of 9

Who bleeds.

Bleeding risk decides most aspirin questions. Every guideline that allows aspirin excludes people at increased bleeding risk.

Pooled trials · ATT 2009 · 95,000 people

Serious vascular events	Major extracranial bleeds
RR 0.88 — 0.51% vs 0.57% a year. Mostly nonfatal heart attacks	RR 1.54 — 0.10% vs 0.07% a year; hemorrhagic stroke 0.04% vs 0.03%

Increased bleeding risk

Prior GI bleed or peptic ulcer
Regular NSAIDs or steroids
Thrombocytopenia
Bleeding at other sites
Coagulopathy
Anticoagulants
Chronic kidney disease
Age over 70

Why the two risks are hard to separate — they share risk factors: in ATT 2009, the main risk factors for coronary disease also predicted bleeding. And age raises both: per USPSTF, CVD risk and bleeding risk, with or without aspirin, increase with age.

Aspirin · 7 of 9

Cancer: a different question.

Colorectal cancer prevention was once a reason to take aspirin. USPSTF no longer cites it. A 2025 trial then found benefit after surgery in selected colorectal cancers.

2010s	Pooled cardiovascular trials. Long-term follow-up of older trials suggested fewer cancer deaths, emerging only after years of use
2018	ASPREE. In adults 70 and older, more cancer deaths with aspirin (HR 1.31), not fewer
2022	USPSTF. The 2016 advice had partly rested on colorectal cancer. In 2022 the Task Force called for more long-term data
2025	ALASCCA. After surgery for colorectal cancer with PI3K pathway alterations, 160 mg a day for 3 years

7.7% vs 14.1% — 3-year recurrence with aspirin vs placebo in PIK3CA hotspot mutations (HR 0.49). NEJM, September 2025.

Why ALASCCA does not change this series — it treats a cancer already found, in patients selected by tumor genetics; that is an oncology decision. It says nothing about healthy adults taking aspirin to prevent a first cancer or heart attack.

Aspirin · 8 of 9

Already taking it?

Guidelines address starting aspirin. Many patients started years ago under older advice, and the evidence on stopping is thinner.

First, confirm the indication

Keep it	Review it
Prior MI, stroke or TIA	No vascular disease; started for prevention
Coronary stent or bypass	Now older, or bleeding risk has risen
Symptomatic peripheral artery disease	Taken without a clear reason

What the guidelines say

USPSTF 2022	Its grades cover starting aspirin, not continuing. When deciding to continue or stop, consider age, CVD and bleeding risk, preferences, and why aspirin was started
USPSTF 2022	Data suggest considering stopping around age 75, as benefit shrinks with age

The case for and against stopping — stop: bleeding risk keeps rising with age, and ASPREE found no benefit in healthy adults over 70. Continue: the stopping advice comes from modeling, not trials, and USPSTF gives it no grade.

Ask what else is in the cabinet — over-the-counter aspirin and NSAIDs are often missing from the medication list.

Aspirin · 9 of 9

The answers.

In primary prevention, aspirin is a narrow, individual decision. The default answer is no.

Slide 1 answers

Consider	52, risk 12%, no bleeding risk — USPSTF grade C: an individual decision
Don't	74, healthy — ASPREE: no benefit, more bleeding; USPSTF grade D
Consider	58, diabetes, smoker — ASCEND and ADA; first, statin and stop smoking
Don't	64, prior ulcer — increased bleeding risk excludes aspirin in every guideline
Review	79, on it for 15 years, no CVD — discuss stopping; USPSTF modeling points to about 75
Don't	48, low risk, daily ibuprofen — low benefit, NSAID adds bleeding risk

If aspirin is chosen

Dose	75 to 100 mg once a day; 81 mg in the US
Revisit	Around 75, and whenever bleeding risk changes

The deciding questions — any vascular disease? If yes, this is secondary prevention and aspirin is indicated. If not: under 60, high risk, low bleeding risk? Only then is it a discussion.

Educational reference only — not medical advice. Verify against local protocol.

Sources

Verify against current guidelines and local protocol before acting.

Antithrombotic Trialists' (ATT) Collaboration. Aspirin in the primary and secondary prevention of vascular disease: meta-analysis of individual participant data from randomised trials. Lancet 2009;373:1849–60.
ASCEND Study Collaborative Group. Effects of aspirin for primary prevention in persons with diabetes mellitus. N Engl J Med 2018;379:1529–39.
Gaziano JM, et al. ARRIVE — use of aspirin to reduce risk of initial vascular events in patients at moderate risk of cardiovascular disease. Lancet 2018;392:1036–46.
McNeil JJ, et al. ASPREE — effect of aspirin on disability-free survival in the healthy elderly. N Engl J Med 2018;379:1499–508; on cardiovascular events and bleeding, 1509–18; on all-cause mortality, 1519–28.
US Preventive Services Task Force. Aspirin use to prevent cardiovascular disease: recommendation statement. JAMA 2022;327:1577–84.
Arnett DK, et al. 2019 ACC/AHA guideline on the primary prevention of cardiovascular disease. Circulation 2019;140:e596–e646.
American Diabetes Association. Standards of Care in Diabetes—2026, Section 10: Cardiovascular disease and risk management. Diabetes Care 2026;49(Suppl 1).
Visseren FLJ, et al. 2021 ESC guidelines on cardiovascular disease prevention in clinical practice. Eur Heart J 2021;42:3227–337.
Martling A, et al. ALASCCA — low-dose aspirin for PI3K-altered localized colorectal cancer. N Engl J Med 2025.
2026 ACC/AHA dyslipidemia guideline (PREVENT risk equations).

Downloads

Every card behind this topic, as published — view full size or download.

Carousel9 slides