Groundbreaking new research has revealed a direct and measurable link between obesity and a significantly faster progression of Alzheimer's disease. The study, presented at the Radiological Society of North America (RSNA) Annual Meeting, found that key proteins associated with the memory-robbing condition increased up to 95% faster in obese individuals showing early signs of Alzheimer's.
Blood Tests Uncover a Hidden Link
Researchers from Washington University School of Medicine conducted a five-year analysis of 407 participants from the Alzheimer's Disease Neuroimaging Initiative. They compared amyloid positron emission tomography (PET) brain scans with plasma blood samples, testing for biomarkers like neurofilament light chains and pTau217.
Dr Cyrus Raji, a radiology and neurology expert involved in the study, stated: 'This is the first time we've shown the relationship between obesity and Alzheimer's disease as measured by blood biomarker tests.' He emphasised the profound implications, noting that powerful obesity drugs could now be tracked for their effect on Alzheimer's progression in future trials.
Why Initial Scans Can Be Misleading
Intriguingly, the study initially suggested that a higher Body Mass Index (BMI) was linked to lower levels of Alzheimer's biomarkers in the blood. Lead researcher Dr Soheil Mohammadi explained this paradox: 'We believe the reduced blood biomarkers in obese individuals was due to dilution from the higher blood volume.'
This means that relying on a single snapshot could falsely indicate lower disease pathology in obese people. Only by tracking changes over time—longitudinal data—did the true, accelerating effect of obesity become clear.
The Striking Acceleration Figures
The longitudinal analysis yielded stark results. Participants classified as obese (BMI 30-39.9) experienced a 29% to 95% faster rate of increase in pTau217 levels compared to those of a healthy weight.
Furthermore, obesity at the study's start was associated with a 24% quicker release of protein fragments from damaged neurons and nearly a 4% faster build-up of amyloid plaques in the brain.
A New Era for Monitoring and Prevention
The research team concluded that blood tests are more sensitive than PET scans in capturing obesity's impact on Alzheimer's risk. Dr Raji expressed astonishment at this finding, stating blood biomarkers could more sensitively track obesity's predictive influence.
This work underscores maintaining a healthy weight as a critical, modifiable defence against dementia. Dr Mohammadi highlighted the 2024 Lancet Commission report, which found that 14 modifiable risk factors account for roughly 45% of Alzheimer's risk. Targeting these, including obesity, could significantly reduce cases or delay onset.
The findings pave the way for routine blood biomarker tests, combined with MRI scans, to become standard for monitoring disease progression and tailoring treatments.
The Weight Loss Drug Horizon
The study arrives alongside promising, yet complex, research into weight loss medications. Separate British research has suggested the GLP-1 drug liraglutide (Saxenda)—already prescribed for obesity on the NHS—could slash Alzheimer's risk and slow cognitive decline by up to 50%.
However, recent trial results for another drug, semaglutide, showed it did not slow Alzheimer's progression, highlighting the need for more research. The connection between obesity, dementia, and pharmaceutical interventions remains a vital and active frontier in medical science.
With nearly one million people living with dementia in the UK, and Alzheimer's constituting around 60% of cases, understanding and mitigating risk factors has never been more urgent.
