# Proof Narrative: Daily low-dose aspirin reduces the risk of recurrent non-fatal myocardial infarction in patients with prior cardiovascular disease, per the Antithrombotic Trialists' Collaboration meta-analysis

## Verdict

**Verdict: PROVED**

The named source — the Antithrombotic Trialists' Collaboration meta-analysis — does report exactly what the claim says, and the evidence behind it is the strongest kind medicine has.

## What Was Claimed?

The claim has two parts wrapped together. First, a medical statement: people who already have heart or vascular disease, and who take a daily low dose of aspirin, are less likely to have another non-fatal heart attack. Second, an attribution: this finding comes from a specific, famous body of research — the Antithrombotic Trialists' Collaboration, an academic group that has pooled the world's aspirin trials into large meta-analyses.

This matters because aspirin for the heart is one of the most widely used preventive treatments in the world, and because the claim points to a particular evidence source rather than just asserting a general belief. Checking it means checking both whether the effect is real and whether that source actually says so.

## What Did We Find?

The word "reduces" is a cause-and-effect word, so the claim was split into two questions that both had to be answered yes. Is aspirin *linked* to fewer repeat heart attacks in these patients? And is that link genuinely *causal*, rather than a coincidence?

On the first question, the Collaboration's 2002 analysis — which pooled 287 trials and roughly 135,000 high-risk patients — found that among those patients, non-fatal heart attacks were cut by about one third. The same analysis confirmed that low doses of aspirin, in the familiar 75–150 mg range, worked at least as well as higher doses, so the finding applies to ordinary "low-dose" aspirin and not just to large doses. The Collaboration's later 2009 analysis, looking specifically at patients who already had vascular disease, independently confirmed the direction: aspirin produced a clear reduction in serious vascular events.

On the second question, the answer comes from how the research was built. The Collaboration only pooled randomized controlled trials — studies where patients are assigned aspirin or no aspirin by chance. Random assignment is what lets researchers say a treatment *caused* a difference rather than merely accompanied it. Both the 2002 and 2009 analyses are explicitly built from randomized trials, so the reduction is causal evidence, not just correlation.

Every quotation used was pulled directly from the original published papers, hosted on U.S. National Institutes of Health websites, and checked word-for-word. All five checked out. Counter-arguments were also tested: aspirin's well-known bleeding risk, recent debate about whether aspirin still matters as much in an era of statins and stents, and the question of whether "recurrent" was a fair word. None of them overturned the finding — they qualify how aspirin is used today, but not whether the Collaboration found this reduction.

## What Should You Keep In Mind?

This proof confirms a narrow, specific thing: that the Antithrombotic Trialists' Collaboration meta-analysis found low-dose aspirin reduces recurrent non-fatal heart attacks in people with established cardiovascular disease. It is **not** a verdict that aspirin is the best choice for every such patient today. Aspirin also increases the risk of serious bleeding, and newer drugs and treatments have changed the picture — whether aspirin's benefit outweighs its risks for any individual is a separate clinical question this proof does not answer. The finding is also strong precisely for *secondary* prevention (people who already have disease); aspirin for *primary* prevention in healthy people is a genuinely contested area and is outside this claim. Anyone making a personal decision about aspirin should talk to a doctor.

## How Was This Verified?

The claim was decomposed into an association part and a causation part, each backed by verbatim quotations fetched live from the original journal articles and confirmed character-for-character; counter-evidence was searched for and weighed. You can read [the structured proof report](proof.md), inspect [the full verification audit](proof_audit.md), or [re-run the proof yourself](proof.py).
