Cited by 3,675Antiplatelet Therapy and Cardiovascular DiseasesInflammatory mediators and NSAID effectsAcute Ischemic Stroke Management

Aspirin in the primary and secondary prevention of vascular disease: collaborative meta-analysis of individual participant data from randomised trials

Open access
Antithrombotic Trialists' (ATT) Collaboration·2009·The Lancet

Abstract

Background Low-dose aspirin is of definite and substantial net benefit for many people who already have occlusive vascular disease. We have assessed the benefits and risks in primary prevention.Methods We undertook meta-analyses of serious vascular events (myocardial infarction, stroke, or vascular death) and major bleeds in six primary prevention trials (95,000 individuals at low average risk, 660,000 person-years, 3554 serious vascular events) and 16 secondary prevention trials (17,000 individuals at high average risk, 43,000 person-years, 3306 serious vascular events) that compared long-term aspirin versus control. We report intention-to-treat analyses of first events during the scheduled treatment period.Findings In the primary prevention trials, aspirin allocation yielded a 12% proportional reduction in serious vascular events (0.51% aspirin vs 0.57% control per year, p=0.0001), due mainly to a reduction of about a fifth in non-fatal myocardial infarction (0.18%vs 0.23% per year, p<0.0001). The net effect on stroke was not significant (0.20%vs 0.21% per year, p=0.4: haemorrhagic stroke 0.04%vs 0.03%, p=0.05; other stroke 0.16%vs 0.18% per year, p=0.08). Vascular mortality did not differ significantly (0.19%vs 0.19% per year, p=0.7). Aspirin allocation increased major gastrointestinal and extracranial bleeds (0.10%vs 0.07% per year, p<0.0001), and the main risk factors for coronary disease were also risk factors for bleeding. In the secondary prevention trials, aspirin allocation yielded a greater absolute reduction in serious vascular events (6.7%vs 8.2% per year, p<0.0001), with a non-significant increase in haemorrhagic stroke but reductions of about a fifth in total stroke (2.08%vs 2.54% per year, p=0.002) and in coronary events (4.3%vs 5.3% per year, p<0.0001). In both primary and secondary prevention trials, the proportional reductions in the aggregate of all serious vascular events seemed similar for men and women.Interpretation In primary prevention without previous disease, aspirin is of uncertain net value as the reduction in occlusive events needs to be weighed against any increase in major bleeds. Further trials are in progress.Funding UK Medical Research Council, British Heart Foundation, Cancer Research UK, and the European Community Biomed Programme.

The claims and statistics of this paper haven’t been checked yet.

Run the check — free, no account needed. It reads the open-access text and checks the sources it cites.

A few free checks a day · papers already verified open instantly · results are public

Integrity signals

Registry

Crossref · 10.1016/s0140-6736(09)60503-1

Cites

31 of 31 references verified0 citation errors · 0 not checkable

Statistics

Claims the paper makes

The claims and statistics of this paper haven’t been checked yet.

Run the check — free, no account needed. It reads the open-access text and checks the sources it cites.

A few free checks a day · papers already verified open instantly · results are public

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • In the meta-analysis, the higher relative risk of bleeding with aspirin use than with control was similar among persons with diabetes and those without diabetes.

    “Likewise, the higher relative risk of bleeding with aspirin use than with control was similar among persons with diabetes and those without diabetes.”

    From Effects of aspirin for primary prevention in persons with diabetes mellitus (2018) · cites this paper as [1]

    The Results report a higher relative risk of major gastrointestinal and other extracranial bleeding with aspirin than with control in the primary prevention trials (RR 1.54). They also identify diabetes among risk factors associated with bleeding, but the passages do not compare aspirin’s bleeding relative risk between people with and without diabetes. Searches for a diabetes-specific bleeding comparison did not establish the claimed similarity; page numbers were not provided in our copy. (LLM, conf=0.84)

    Experimental — accuracy not yet measured
  • In the meta-analysis, the lower relative risk of serious vascular events among participants with diabetes was similar to that among participants without diabetes.

    “Only approximately 4% of participants in those trials had diabetes, and the lower relative risk among them was similar to that observed among participants without diabetes (as was also observed in the context of secondary prevention).”

    From Effects of aspirin for primary prevention in persons with diabetes mellitus (2018) · cites this paper as [1]

    The Discussion (page unavailable) says that, in the primary-prevention trials, the proportional reduction in serious vascular events did not differ significantly by history of diabetes. This supports the main comparison, but the passages do not establish the citing sentence’s approximately 4% figure or its diabetes-specific comparison in secondary prevention. (LLM, conf=0.82)

    Experimental — accuracy not yet measured
  • The lower risk of serious vascular events with aspirin is similar to the risk reported previously in the Antithrombotic Trialists' Collaboration meta-analysis of primary prevention trials of similar doses of aspirin, which used slightly different outcome definitions.

    “The lower risk of serious vascular events is similar to the risk that was reported previously in the Antithrombotic Trialists' Collaboration meta-analysis of primary prevention trials of similar doses of aspirin (which used slightly different outcome definitions”

    From Effects of aspirin for primary prevention in persons with diabetes mellitus (2018) · cites this paper as [1]

    Split into 2 atoms — 1 confirmed, 0 partially supported, 0 disputed, 0 misattributed, 1 unverifiable. Expand the claim to see per-atom verdicts.

    Experimental — accuracy not yet measured
  • In the Antithrombotic Trialists' Collaboration meta-analysis, the largest reduction was for nonfatal MI, with little effect on CHD death (relative risk 0.95 [95% CI 0.78-1.15]) or total stroke.

    “The largest reduction was for nonfatal MI, with little effect on CHD death (relative risk 0.95 [95% CI 0.78-1.15])or total stroke.”

    From 10. Cardiovascular Disease and Risk Management: Standards of Care in Diabetes—2025 (2025) · cites this paper as [178]

    The Results report that, in primary prevention trials, the reduction in coronary events came mainly from nonfatal MI, with no clear reduction in CHD death; the net effect on stroke was not significant. But the quoted interval for CHD death is a 99% CI, not a 95% CI, and the sentence omits the primary-prevention restriction: the paper reports a significant reduction in total stroke in secondary prevention trials (Findings). (LLM, conf=0.90)

    Experimental — accuracy not yet measured
  • In that meta-analysis, the largest reduction was for nonfatal MI, with little effect on CHD death (relative risk 0.95 [95% CI 0.78-1.15]) or total stroke.

    “The largest reduction was for nonfatal MI, with little effect on CHD death (relative risk 0.95 [95% CI 0.78–1.15]) or total stroke.”

    From 10. Cardiovascular Disease and Risk Management: Standards of Care in Diabetes—2026 (2026) · cites this paper as [172]

    The Results report that, in primary prevention trials, the reduction in coronary events came mainly from fewer nonfatal MIs, with no clear reduction in CHD mortality. They give the CHD-death estimate as RR 0.95 with a 99% CI of 0.78–1.15, not the claimed 95% CI. The Results also report no net effect on total stroke in primary prevention, but a significant reduction in total stroke in secondary prevention; the claim omits that distinction. (LLM, conf=0.90)

    Experimental — accuracy not yet measured

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

The self-check needs the paper’s full text.

Cites

Flagged first, then by citations

Cited by

Sorted by citations

Authors
Antithrombotic Trialists' (ATT) Collaboration
Corresponding author
Antithrombotic Trialists' (ATT) Collaboration
Venue
The Lancet
Publisher
Elsevier BV
Published
2009-05
Volume
373
Issue
9678
Pages
1849-1860
ISSN
  • 0099-5355 (ISSN-L)
  • 0140-6736
OpenAlex
W2100089051
Cited by
3,675
References
31
Citations by year
2026: 84 · 2025: 142 · 2024: 165 · 2023: 208 · 2022: 194 · 2021: 222 · 2020: 233 · 2019: 250 · 2018: 218 · 2017: 244 · 2016: 232 · 2015: 235 · 2014: 233 · 2013: 246 · 2012: 278
FWCI
38.00
Type
journal article
Language
en
Open access
Locations
  • The Lancet (publishedVersion)
  • Europe PMC (PubMed Central) (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
  • ResearchOnline (acceptedVersion)
  • LSHTM Research Online (London School of Hygiene and Tropical Medicine) (submittedVersion)
  • ResearchOnline (Glasgow Caledonian University) (submittedVersion)
Funders
  • AstraZeneca
  • Brigham and Women's Hospital
  • Harvard University
  • Florida Atlantic University
  • London School of Hygiene and Tropical Medicine
  • Università degli Studi di Milano
  • Universidad del Atlántico
  • Cancer Research UK
  • British Heart Foundation
  • University of Oxford
  • Trinity College Dublin
  • Istituto Auxologico Italiano
  • Medical Research Council
Topics
  • Health Sciences › Medicine › Cardiology and Cardiovascular Medicine › Antiplatelet Therapy and Cardiovascular Diseases
  • Health Sciences › Medicine › Pharmacology › Inflammatory mediators and NSAID effects
  • Health Sciences › Medicine › Epidemiology › Acute Ischemic Stroke Management
Keywords
aspirin, low-dose aspirin, primary prevention, secondary prevention, vascular disease, myocardial infarction, stroke, vascular death, major bleeding, gastrointestinal bleeding, hemorrhagic stroke, coronary events, bleeding risk, individual patient data, cardiovascular risk factors, net benefit, coronary artery disease, stroke prevention, vascular risk reduction, bleeding risk reduction, cardiovascular disease prevention
MeSH terms
Aspirin, Cardiovascular Diseases, Cause of Death, Female, Fibrinolytic Agents, Hemorrhage, Humans, Male, Primary Prevention, Research Design, Risk Factors, Randomized Controlled Trials as Topic, Treatment Outcome, Practice Guidelines as Topic, Sex Distribution, Risk Assessment, Patient Selection, Risk Reduction Behavior, Secondary Prevention

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

Are you an author, or do you see a problem with this page? Request a review