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How do I convert the SOUL hazard ratio into an absolute risk reduction?

Asked 8 Jun 2025Modified 10 months agoViewed 7.8k times
3

I have three data points across nine months, which I hope is enough to see a trend.

I would like the arithmetic checked rather than the conclusion asserted.

I have deliberately not used an online calculator because I want to be able to check the result.

Can someone walk through the arithmetic step by step?

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IB
askedilaria_bertone33k388 Jun 2025
5Which trial, and which endpoint? The question is answerable once those are named. – kwn_analytical 2 months ago
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5 Answers

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66

It helps to be literal here: heart-rate increase and blood-pressure reduction both occur in this class, in opposite directions, and both are modest. Reading one without the other gives a misleading picture.

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.

The relevant detail is that 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.

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.

The caveat that matters: none of this is a reason for anyone to alter cardiovascular medication, and I am not in a position to advise on that.

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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DB
answeredDr_Ingrid_Baumgartner73k5827 Jun 2025
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45

Blood pressure falls by a few millimetres of mercury in this class, which is small individually and not small across a population.

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.

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.

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

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DV
answeredDr_Ilse_Vandenberg113k24816 Jun 2025
32

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.

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.

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.

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

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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MF
answeredmeniscus_film32k273 Oct 2025
26

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

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.

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.

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.

edited 11 Oct 2025 by RP_C18 — updated for the 2026 guidance change

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RC
answeredRP_C18105k34822 Sept 2025
6The number needed to treat is the framing that finally made this concrete for me. – Dr_Yusuf_Adeyemi 9 months ago
7The exclusion criteria are the most informative page in the supplement and nobody reads them. – loss_on_drying 17 days ago
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24

Answering this properly needs the absolute risk reduction rather than the relative one, because the relative figure is stable across risk strata and the absolute figure is not.

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.

A relative risk reduction quoted without the baseline risk is close to meaningless, and it is how most of these numbers travel.

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

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DV
answeredDr_Ilse_Vandenberg113k24811 Sept 2025
Good answer, but the confidence interval in the cited trial is wider than implied. – m_haraldsen 6 months ago
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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.