Why researchers looked at GLP-1 medicines

Diabetes, obesity and cardiovascular disease can influence long-term brain health. GLP-1 receptor agonists improve blood-sugar regulation and can reduce weight and cardiovascular risk in appropriately selected patients. Laboratory research has also explored effects on inflammation and cellular signalling in the nervous system.

These overlapping pathways created a biologically plausible question: could a medicine developed for metabolic disease also reduce the risk or progression of neurodegeneration? Plausibility, however, is the beginning of a research question—not proof of a clinical benefit.

What the observational study suggested

A large analysis of electronic health records in people with type 2 diabetes found that semaglutide use was associated with fewer first-time Alzheimer’s diagnoses than several other diabetes medications. The association was substantial enough to justify dedicated clinical trials.

Because treatment was not randomly assigned, the groups may have differed in health status, weight change, access to care, prescribing patterns and other factors. The study therefore identified an association; it did not show that semaglutide prevented Alzheimer’s disease.

What EVOKE and EVOKE+ tested

EVOKE and EVOKE+ were phase 3, randomized, placebo-controlled trials involving 3,808 adults aged 55 to 85 with amyloid-confirmed mild cognitive impairment or mild dementia due to Alzheimer’s disease. Participants at 566 sites across 40 countries received oral semaglutide, at a flexible dose up to 14 mg, or placebo.

The primary question was whether semaglutide could slow change in cognition and daily function after 104 weeks. Random assignment and placebo comparison made these trials better suited than health-record studies to determine whether the medication itself produced a clinical benefit.

What the trials found

Semaglutide did not significantly slow cognitive or functional decline in either trial. It also did not delay progression from mild cognitive impairment to dementia, and secondary measures of cognition did not show a meaningful clinical advantage over placebo.

Some biological markers of inflammation and Alzheimer’s-related processes changed, but those changes did not translate into better memory, thinking or daily function during the trials. Treatment discontinuation due to adverse effects was more common with semaglutide, mainly because of gastrointestinal symptoms, reduced appetite and weight loss.

Why the findings can look different

Observational studies ask what happened in routine care, while randomized trials test whether an intervention caused an outcome under controlled conditions. A medication can appear protective in health records because of differences between the people who did and did not receive it—even after researchers adjust for many known factors.

The findings also answer different questions. The observational study examined first-time Alzheimer’s diagnoses among people with type 2 diabetes. EVOKE and EVOKE+ examined disease progression after early symptomatic Alzheimer’s disease was already present. The randomized results do not settle every prevention question, but they do show that oral semaglutide should not be presented as a treatment that slows established early Alzheimer’s disease.

Study authors and funding

The Lancet report was authored by Jeffrey L. Cummings, Alireza Atri, Howard H. Feldman, Mary Sano, Henrik Zetterberg, Filip K. Knop, Peter Johannsen, Teresa León, Rikke Mortensen Abschneider and Philip Scheltens.

The EVOKE and EVOKE+ trials were sponsored and funded by Novo Nordisk A/S, the manufacturer of semaglutide. Sponsor involvement and author disclosures are reported in the complete publication linked below and should be considered when interpreting the results.