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What is the reported incidence of headache on semaglutide in STEP 2?

Asked 6 Mar 2026Modified 2 months agoViewed 3.2k times
5

Setup, so nobody has to ask: headache · semaglutide · STEP 2.

I have read the primary source rather than the summary, which has left me with more questions.

I understand the headline. I do not understand the footnotes, and the footnotes look important.

What would I need in addition before this supported a decision?

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HV
askedhelena_vidmar8.5k276 Mar 2026

2 Answers

Accepted answer first, then by votes
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Accepted answer

Take it from the STEP 2 adverse-event table by arm, and check the unit before you use it. An incidence can be the proportion of participants who reported the event at least once, or the count of events divided by exposure time, and the two differ by however many people had it repeatedly. Then subtract the placebo arm, because the untreated rate is not zero. And read the discontinuation column beside it: an event that made people leave the trial is under-counted at every later visit, so a low late-timepoint incidence can mean the event was severe rather than rare.

Start with what the trial was powered for. Everything else in the publication is secondary, exploratory, or a subgroup, and those three words mean three different things.

Placebo arms in this class are not nothing. Lifestyle-intervention placebo arms in the major obesity trials commonly lose two to three per cent of body weight, so an active-arm figure quoted without its comparator overstates the drug effect by roughly that much.

Intention-to-treat and per-protocol analyses answer different questions. ITT asks what happens if you offer the treatment; per-protocol asks what happens if it is taken as directed. The gap between the two is a measure of how tolerable the protocol was.

Where a result is quoted from a conference abstract rather than a peer-reviewed publication, the numbers routinely move between the two. It is worth checking which one you are reading.

I am not a clinician and this is not medical advice; it is a reading of a published protocol.

If a claim cannot be traced to a named trial with a named endpoint, treat it as a claim rather than as evidence.

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DB
answered · acceptedDr_Ingrid_Baumgartner73k5828 Apr 2026
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The short version: the effect is real, the magnitude depends on the population, and the population is usually the part that gets dropped when a result is quoted second-hand.

Open-label extensions are not the same evidence as the randomised phase. Once everyone knows what they are taking, the reported outcomes acquire a bias that no analysis fully removes.

Non-inferiority and superiority designs are not interchangeable. A non-inferiority result says the new agent is not meaningfully worse against a pre-specified margin — it does not say it is as good, and it certainly does not say it is better.

The caveat is that trial evidence is about licensed product administered under supervision. None of it transfers automatically to research-grade material of unverified content.

Quote the interval alongside the estimate and half the disagreements on this site would not start.

edited 6 Jun 2026 by h_villanueva — removed a claim I could not source

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HV
answeredh_villanueva70k4810 May 2026
2I would gently push back — that was a secondary endpoint, not the primary one. – e_dziedzic 4 days 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.