Cerebral oxygen extraction fraction as a physiological biomarker in vascular cognitive impairment: A study in older adults enriched for small vessel diseases.
Song J, Shi W, et al. • Alzheimer's & dementia : the journal of the Alzheimer's Association • 2026
Elevated cerebral oxygen extraction fraction (OEF) is associated with poorer cognition and greater vascular burden in older adults with vascular risk factors, suggesting OEF is a physiological biomarker for vascular cognitive impairment and dementia (VCID).
Key Findings
Results
Poorer global cognition was significantly associated with elevated OEF in older adults enriched for small vessel diseases.
Study sample consisted of 81 older adults with at least one vascular risk factor.
OEF was quantified in major cerebral veins using magnetic resonance imaging.
Global cognition was assessed using a composite score across multiple cognitive domains.
The association between OEF and global cognition remained significant after controlling for AD co-pathology as measured by plasma phosphorylated tau 217 (p-tau217).
Results
Poorer executive function was significantly associated with elevated OEF in this VCID-enriched cohort.
Executive function was evaluated as a distinct cognitive domain in addition to global cognition.
The association between OEF and executive function was independent of plasma AD biomarkers.
Executive function impairment is a hallmark feature of vascular cognitive impairment, consistent with the vascular etiology reflected by OEF.
Results
Cognitive impairment in this cohort was not associated with plasma phosphorylated tau 217, distinguishing VCID pathology from Alzheimer's disease co-pathology.
Plasma p-tau217 was used as a marker of AD co-pathology.
Unlike OEF, plasma p-tau217 did not show significant associations with global cognition or executive function in this vascular risk-enriched sample.
This dissociation supports OEF as a biomarker specific to the vascular rather than Alzheimer's pathway of cognitive impairment.
Results
Elevated OEF correlated with a greater number of vascular risk factors.
Participants were required to have at least one vascular risk factor for inclusion in the study.
A higher burden of vascular risk factors was associated with increased OEF, indicating that OEF reflects cumulative vascular disease status.
Vascular risk factors assessed included common conditions such as hypertension, diabetes, and hyperlipidemia.
Results
Elevated OEF was associated with greater white matter hyperintensity (WMH) volume on brain imaging.
White matter hyperintensities are a structural marker of cerebral small vessel disease.
The correlation between OEF and WMH volume links the physiological measure (oxygen extraction) to established structural evidence of small vessel pathology.
This finding supports OEF as a functional complement to existing structural neuroimaging biomarkers of VCID.
Methods
The study recruited a cohort specifically enriched for small vessel diseases by requiring at least one vascular risk factor, and collected comprehensive cognitive, plasma, and imaging data.
Total sample size was 81 older adults.
Data collection included comprehensive cognitive assessments, plasma biomarkers (including p-tau217), and MRI-based imaging.
OEF was specifically measured in major cerebral veins using MRI.
The design allowed simultaneous evaluation of vascular and AD biomarkers to disentangle their independent contributions to cognition.
What This Means
This research suggests that a brain measurement called oxygen extraction fraction (OEF) — which captures how efficiently brain tissue is pulling oxygen from blood flowing through cerebral veins — may serve as a useful biological marker for a condition called vascular cognitive impairment and dementia (VCID). VCID occurs when disease in the brain's small blood vessels reduces blood flow and oxygen delivery, gradually impairing thinking and memory. The study enrolled 81 older adults who had at least one vascular risk factor (such as high blood pressure or diabetes) and used MRI to measure OEF alongside standard cognitive tests and blood-based markers of Alzheimer's disease.
The key finding was that people with higher OEF — meaning their brain tissue was working harder to extract oxygen, a sign that blood supply may be insufficient — performed worse on tests of overall thinking ability and executive function (skills like planning and problem-solving). Importantly, these associations with OEF held even after accounting for Alzheimer's disease-related changes in the blood. In contrast, a blood marker for Alzheimer's disease (phosphorylated tau 217) was not linked to cognitive performance in this group, suggesting the cognitive difficulties in this vascular-risk-enriched sample were more related to vascular problems than Alzheimer's pathology. Higher OEF also correlated with having more vascular risk factors and more white matter damage visible on brain scans.
This research suggests that OEF measured by MRI could be a valuable physiological tool to detect and track vascular contributors to cognitive decline separately from Alzheimer's disease. This distinction matters because VCID and Alzheimer's disease may require different treatment approaches, and current biomarkers are heavily focused on Alzheimer's pathology. Having a reliable, non-invasive vascular biomarker like OEF could improve diagnosis and potentially help evaluate new therapies targeting the vascular causes of cognitive impairment.
Song J, Shi W, Suconic J, Hazel K, Pottanat G, Jones E, et al.. (2026). Cerebral oxygen extraction fraction as a physiological biomarker in vascular cognitive impairment: A study in older adults enriched for small vessel diseases.. Alzheimer's & dementia : the journal of the Alzheimer's Association. https://doi.org/10.1002/alz.71828