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How do I convert the PIONEER-4 hazard ratio into an absolute risk reduction?

Asked 15 May 2026Modified 2 days agoViewed 4.2k times
14

My laboratory results are from the same laboratory each time, drawn fasting, which I gather matters.

Please show the division. I want to check my own against yours.

I would like the general form as well as the specific number, so I can apply it again.

Is my approach right even if my number is wrong?

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askedsyringe_ninety12k1715 May 2026

5 Answers

Accepted answer first, then by votes
11

Accepted answer

A hazard ratio from PIONEER-4 cannot be converted into an absolute risk reduction without the control-arm event rate, and that rate is the number people forget to carry across. The arithmetic: absolute reduction equals the control event rate minus the treated event rate, and the treated rate is approximately the control rate multiplied by the ratio. A hazard ratio of 0.80 against a 10 per cent control rate is a 2-point absolute reduction and a number needed to treat of 50; the same 0.80 against a 2 per cent control rate is 0.4 points and a number needed to treat of 250. Identical ratio, six-fold difference in what it is worth. Take the control-arm rate and the follow-up duration from the PIONEER-4 paper, not from the abstract, and do the subtraction yourself.

More usefully, the relevant distinction is between a trial that measured cardiovascular safety and one powered to demonstrate benefit. Several early trials did the first and are quoted as though they did the second.

The heart-failure question is separate again, and the evidence there is largely in the preserved-ejection-fraction population with obesity, where the trials measured symptoms and function rather than mortality.

Systolic blood pressure falls by about three to six millimetres of mercury at the doses studied, most of it early and much of it attributable to weight loss rather than to a direct vascular effect.

The cardiovascular safety requirement for new glycaemic agents is why these trials exist at all: regulators required an outcome programme, and the benefit finding was in that sense an unexpected dividend.

These are trial populations on licensed product. Research-grade material of unverified content is not the thing that was studied.

Heart rate up a few beats, blood pressure down a few millimetres, events down about a fifth in high-risk populations. That is the honest summary.

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DH
answered · acceptedDr_Jonas_Halvorsen28k3726 May 2026
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15

Mechanically, what the outcome trials established is that the class does not increase cardiovascular risk and, in the higher-risk populations studied, reduces it. Those are two separate findings from the same programme.

Baseline risk decides how much the relative reduction is worth. The same twenty per cent applied to a one per cent annual risk and a five per cent annual risk produce very different absolute numbers.

SELECT randomised people with established cardiovascular disease and overweight or obesity but without diabetes to semaglutide 2.4 mg, and reported roughly a twenty per cent relative reduction in the primary composite. The absolute difference over about three years was on the order of one and a half percentage points.

Where a cardiovascular claim is made for an agent with no completed outcome trial, the honest statement is that the class evidence is suggestive and the agent-specific evidence does not yet exist.

Read SELECT for the without-diabetes population and the earlier outcome trials for the with-diabetes one. They are not the same result.

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DF
answeredDr_Colm_Fitzhenry69k24728 Jul 2026
12

Answer first: the cardiovascular signal in this class is a reduction in major adverse cardiovascular events in populations already at elevated risk, not a general cardioprotective claim for everyone.

A twenty per cent relative reduction on a baseline three-year event rate of eight per cent is an absolute reduction of about one and a half points, which is a number-needed-to-treat somewhere in the region of sixty to seventy. Both framings are true and they read very differently.

The underlying point is that resting heart rate rises by roughly two to four beats per minute across the class. The mechanism is not fully settled, the magnitude is consistent, and it has not translated into an adverse outcome signal in the trials that looked.

SELECT is the trial to read for primary-prevention-adjacent populations without diabetes; SUSTAIN-6 and LEADER are the diabetes-population outcome trials for semaglutide and liraglutide respectively.

Ask for the absolute risk reduction and the number needed to treat. If a source will not give you both, it is selling something.

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DV
answeredDr_Ilse_Vandenberg113k24811 Jul 2026
8

It helps to be literal here: blood pressure falls by a few millimetres of mercury in this class, which is small individually and not small across a population.

Benefit appears to track exposure duration rather than switching on at a threshold, which is what you would expect from a mechanism working partly through weight, blood pressure and glycaemia rather than instead of them.

Heart-rate elevation in this class is documented consistently enough across agents that it should be treated as a class effect rather than as a finding about any one molecule.

Nothing here is medical advice. If cardiovascular risk is the actual question, it is a conversation for a clinician with your numbers in front of them.

Population, baseline risk, endpoint definition. In that order, then the effect size.

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TO
answeredt_oyelaran79k4819 May 2026
2The number needed to treat is the framing that finally made this concrete for me. – tadhg_o_riordan 4 days ago
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4

Start with the population. Cardiovascular benefit in established disease and cardiovascular benefit in primary prevention are different claims supported by different evidence.

Cardiovascular composites in this programme are typically cardiovascular death, non-fatal myocardial infarction and non-fatal stroke. When one component drives the result, that is worth knowing, because the components differ in how much they matter.

SELECT reported a hazard ratio of 0.80 (95% CI 0.72–0.90) for the primary composite major adverse cardiovascular event endpoint with semaglutide 2.4 mg in overweight or obese adults with established cardiovascular disease and without diabetes[1].

The outcome trials are the evidence; the mechanism is still an argument. Cite the first, be careful with the second.

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JF
answeredjuliette_farnese13k3818 Jun 2026

Your answer

Ask PeptideStack is a static archive. Posting is closed, but the norms are worth stating: answer the question that was asked, show your working, cite the trial or the certificate, and say plainly where the evidence runs out.

Not medical advice. Research-use-only compounds are not approved for human use.