Peptide basics

Mean age 46: what GLP-1 weight trials recorded about adults over 65

This page contains no dose, schedule or route, and does not say whether any compound is suitable at any age. It reports how many older adults appear in the trial record, and where those counts are published.

The mean age, and why it is low

STEP 1 posted a mean age of 46 years for its 1,961 randomised adults. SURMOUNT-1 posted 44.9 years for its 2,539. Both trials required participants to be 18 or older and neither set an upper limit.¹⁸

So the young average is a recruitment result, not a rule. Something about who volunteered, who was screened in, and where the sites were produced a database centred on people in their mid-forties.¹⁸

Where the older counts are actually published

The registry posts a mean age but not an age band breakdown for these trials. The count of older patients appears instead in the geriatric use section of the approved US labeling, which sponsors are required to complete.¹²

For semaglutide in weight management, that section records 233 treated patients (8.8%) between 65 and 75 years of age and 23 (0.9%) aged 75 or over, and states that no overall differences in safety or efficacy were detected between these patients and younger patients, while adding that greater sensitivity of some older individuals cannot be ruled out.²

The tirzepatide label records 226 treated patients (9%) aged 65 or over and 13 (0.5%) aged 75 or over at baseline. The liraglutide weight-management label records 232 treated patients (6.9%) aged 65 and over and 17 (0.5%) aged 75 and over.³⁴

• Semaglutide (weight management): 233 aged 65-75, 23 aged 75 or over.
• Tirzepatide: 226 aged 65 or over, 13 aged 75 or over.
• Liraglutide (weight management): 232 aged 65 or over, 17 aged 75 or over.²³⁴

Measured against the published benchmark

ICH E7, the international guideline on geriatric populations, defines that population as patients aged 65 or older and says it is important to seek patients in the older range, 75 and above, to the extent possible. It also states that protocols should not ordinarily include arbitrary upper age cutoffs.⁵

For a drug used in diseases not unique to but present in older people, the guideline says a minimum of 100 such patients would usually allow detection of clinically important differences. All three weight-management programmes clear that threshold for the 65-and-over group as a whole.⁵²³⁴

None of them come close for the 75-and-over group. Twenty-three, thirteen and seventeen participants are not sample sizes from which a difference in safety or effect could be detected, and the labels do not claim otherwise.²³⁴⁵

Where the older evidence does exist

The picture changes entirely outside the weight-management indication. SELECT, the cardiovascular outcomes trial of semaglutide, posted a mean age of 61.6 years across 17,604 participants and required a minimum age of 45 rather than 18.⁶

That is 15 years older than STEP 1 and nine times the number of participants. It is the same compound, so anyone looking for evidence in an older population has somewhere to look — but the outcomes measured there were cardiovascular, not weight-management endpoints.¹⁶

Semaglutide is the only compound in this group with both a young weight-management database and a large older cardiovascular database. Which of the two a claim is drawn from determines the age of the people it describes.

The mismatch with who uses them

KFF's May 2024 poll of 1,479 US adults found reported use highest among adults aged 50 to 64, at about 19% ever having taken a GLP-1 drug — higher than any other age group.⁷

Among adults 65 and over, 8% said they had taken one for a chronic condition and 1% for weight loss only, which the pollsters noted may reflect Medicare's exclusion of coverage for drugs prescribed for weight loss.⁷

So the age band with the highest reported use, 50 to 64, sits above the mean age of every pivotal obesity trial, and the band above it is where the trial evidence is thinnest.¹²⁷

Common questions