Obesity drugs may help protect memory and cognitive abilities - News-Medical

A wave of recent coverage from outlets including DongA Science, Earth.com, and News-Medical explores whether GLP-1 obesity medications can protect memory and cognitive abilities. These drugs, such as semaglutide and dulaglutide, are widely used for weight loss and blood sugar control, and some observational studies suggest they may reduce dementia risk. The University of Copenhagen review, led by Stina Börchers and Christoffer Clemmensen, analyzed nearly 200 preclinical studies and major clinical trials, finding the evidence for cognitive benefits complicated and inconclusive.

Insurance database analyses show that type 2 diabetes patients using GLP-1 receptor agonists develop dementia at lower rates than those on other therapies. The REWIND trial reported a 14% lower hazard of cognitive decline with dulaglutide, though cognition was an exploratory outcome and the finding came from post hoc adjustments. A meta-analysis of five randomized trials involving 7,732 adults found no clear improvement in global cognitive performance.

Alzheimer’s-specific trials have been more disappointing. The ELAD study tested liraglutide in 204 people with mild-to-moderate Alzheimer’s for one year, finding some MRI and secondary cognitive improvements but no significant effects on daily functioning or clinical severity. Larger phase 3 trials EVOKE and EVOKE+ enrolled 3,808 participants with mild cognitive impairment or early Alzheimer’s, testing oral semaglutide at 14 mg daily versus placebo for two years. The drug did not slow decline on the Clinical Dementia Rating scale or improve daily functioning, though it reduced cerebrospinal fluid biomarkers phosphorylated tau and neurogranin by roughly 10%.

Researchers note GLP-1 receptors are present in brain regions linked to cognition, including the hippocampus and prefrontal cortex. Preclinical studies show effects on synaptic plasticity and neurotrophic pathways like CREB and BDNF. However, these drugs are large peptides that do not easily cross the blood-brain barrier, reaching only circumventricular organs and parts of the brainstem. Whether they achieve relevant concentrations in the hippocampus remains uncertain.

Potential cognitive benefits may be indirect, stemming from metabolic improvements such as better blood sugar control, reduced inflammation, improved sleep, and cardiovascular protection. Semaglutide reduced cardiovascular events by 20% in the SELECT trial and major kidney outcomes by 24% in FLOW. Tirzepatide showed dramatic improvements in obstructive sleep apnea in SURMOUNT-OSA trials. These systemic benefits could indirectly support brain health, but disentangling direct versus indirect effects is challenging.

Side effects like rapid weight loss, muscle mass reduction, fatigue, dehydration, and malnutrition could offset cognitive gains, particularly in frail older adults. The review calls for trials tracking body composition, nutritional status, and tolerability alongside cognition. Newer combination therapies targeting GLP-1 with GIP, glucagon, or amylin pathways aim to enhance efficacy while reducing side effects. Brain-penetrant peptides and small-molecule agonists may eventually bypass the blood-brain barrier. The OxSENSE study is testing semaglutide’s acute effects on reward sensitivity, memory, and emotional processing in healthy adults.

Science magazine’s special issue emphasizes that while GLP-1 drugs have revolutionized obesity treatment, rigorous clinical trials and long-term safety studies are needed to confirm effects on brain health, addiction, and cancer. Access disparities due to high drug costs remain a key challenge.