Summary: New longitudinal research finds that blood biomarkers for Alzheimer’s disease rise substantially faster in people with obesity than in those without. Although initial blood tests appeared lower in individuals with higher body mass index (BMI) — likely due to dilution from larger blood volume — five-year tracking revealed a markedly accelerated accumulation of markers for neurodegeneration and amyloid pathology in people with obesity.
Blood biomarkers proved more sensitive than brain amyloid PET scans in detecting the impact of obesity on disease progression. These results add weight to the growing evidence that weight management may be an important strategy to reduce or delay Alzheimer’s disease risk.
Key Facts
- Accelerated biomarkers: Obesity was associated with a 29%–95% faster increase in Alzheimer’s-related blood biomarkers over five years.
- Hidden early risk: Baseline blood tests tended to underestimate disease burden in people with obesity, likely because higher blood volume diluted biomarker levels.
- Clinical sensitivity: Blood biomarkers outperformed amyloid PET brain scans in detecting obesity-driven changes in Alzheimer’s pathology.
Source: RSNA
Overview of the study
This is the first study to evaluate how obesity affects Alzheimer’s disease blood biomarkers (BBMs) using longitudinal data. Presented at the Radiological Society of North America (RSNA) annual meeting, the study analyzed five years of data from 407 participants enrolled in the Alzheimer’s Disease Neuroimaging Initiative. The dataset included repeated plasma samples and amyloid positron emission tomography (PET) scans, enabling the team to compare blood biomarker trajectories with brain amyloid accumulation over time.
Investigators measured multiple plasma markers linked to Alzheimer’s pathology: pTau217 (a phosphorylated tau species used in diagnosis and monitoring), neurofilament light chain (NfL), a marker of neuronal injury, and plasma GFAP, a protein associated with astrocyte activation. Measurements were performed using six leading commercial assays, and statistical models assessed how baseline obesity, time, and BBM levels interacted, with validation against amyloid PET imaging.
At baseline, higher BMI correlated with lower measured BBM levels and a reduced estimate of whole-brain amyloid burden on PET. The study authors interpret this counterintuitive finding as a dilution effect: greater blood volume in people with obesity can lower the concentration of circulating biomarkers, producing deceptively low initial values.
Longitudinal findings
When analyzed longitudinally, the picture changed. Over the five-year follow-up, people with obesity showed significantly faster increases in Alzheimer’s-related biomarkers and in brain amyloid accumulation compared with non-obese participants. Specifically, those with obesity experienced a 29% to 95% faster rate of rise in plasma pTau217 ratio levels, a 24% faster increase in plasma NfL, and a 3.7% faster rate of amyloid accumulation on PET. These results indicate that obesity may accelerate both neurodegeneration and amyloid pathology when tracked over time.
The investigators highlighted that blood biomarker measures were more sensitive than PET imaging for capturing the influence of obesity on Alzheimer’s biology. Because blood tests are less invasive and easier to repeat than PET scans, these BBMs could play a central role in monitoring disease progression and evaluating interventions aimed at reducing risk.
Clinical and research implications
The authors stress the importance of longitudinal monitoring to understand how obesity affects Alzheimer’s disease development. Relying on single baseline biomarker readings may miss or misrepresent underlying pathology in people with higher BMI. The findings also align with broader public health evidence: the 2024 Lancet Commission report lists multiple modifiable risk factors that together account for roughly half of Alzheimer’s risk. Targeting those factors, including obesity, could meaningfully reduce future cases or delay onset.
Researchers noted that effective weight-loss treatments available today create opportunities for future studies to test whether losing weight or treating obesity influences Alzheimer’s biomarkers. Longitudinal blood biomarker assessment combined with brain imaging offers a practical framework for tracking treatment effects in clinical trials.
Lead authors include Cyrus Raji, M.D., Ph.D., and Soheil Mohammadi, M.D., M.P.H., with co-authors Farzaneh Rahmani, M.D., M.P.H., Mahsa Dolatshahi, M.D., M.P.H., and Suzanne E. Schindler, M.D., Ph.D.
Key questions answered
A: Yes. Over time, people with obesity show a substantially faster rise in blood biomarkers associated with Alzheimer’s pathology.
A: In this study, blood biomarkers were more sensitive than amyloid PET scans at detecting obesity-related progression.
A: Longitudinal data from this cohort indicate faster accumulation of both amyloid plaques and markers of neurodegeneration in people with obesity.
Editorial notes
- This article was edited by a Neuroscience News editor.
- The underlying journal paper was reviewed in full by the editorial team.
- Additional context was provided by staff to clarify clinical and research implications.
About this research
Author: Linda Brooks
Source: RSNA
Contact: Linda Brooks – RSNA
Image: The image is credited to Neuroscience News
Original research presentation: Findings were presented at the 111th Scientific Assembly and Annual Meeting of the Radiological Society of North America (RSNA).