Subtle alterations in the way blood circulates through the brain and how brain tissue uses oxygen may be closely associated with the risk of Alzheimer’s disease, according to new research from the Mark and Mary Stevens Neuroimaging and Informatics Institute (Stevens INI) at the Keck School of Medicine of the University of Southern California. The findings suggest that changes in the brain’s vascular system may be detectable before clear symptoms of cognitive decline appear. Researchers believe that examining these early physiological signals could help scientists better understand the earliest stages of Alzheimer’s disease and potentially identify individuals who are at greater risk long before memory problems become noticeable.
The study, published in Alzheimer’s and Dementia: The Journal of the Alzheimer’s Association, examined whether noninvasive measures of brain blood flow and oxygenation were linked to biological features commonly associated with Alzheimer’s disease. The researchers analysed older adults both with and without cognitive impairment and compared vascular measurements with established brain markers of the disease. They discovered that these measures were related to key changes such as the accumulation of amyloid proteins and reductions in the size of the hippocampus, a region of the brain that plays a central role in memory. These findings support the idea that vascular health may influence the earliest stages of Alzheimer’s development.
Scientists have traditionally focused on proteins such as amyloid and tau as the primary drivers of Alzheimer’s disease. Still, growing evidence suggests that the brain’s blood supply and oxygen delivery also play an important role. The lead author of the study explained that the results indicate a strong relationship between healthy vascular function and better indicators of cognitive health. When blood vessels in the brain behaved in ways more typical of healthy ageing, researchers also observed brain features that were associated with a lower likelihood of cognitive decline. This connection highlights the possibility that maintaining healthy blood flow to the brain could be important for protecting long-term brain function.
To examine these processes, the research team used two noninvasive technologies that can monitor brain physiology while participants rest quietly. One technique, transcranial Doppler ultrasound, measures the speed at which blood travels through the brain’s major arteries. The other method, near-infrared spectroscopy, detects how effectively oxygen reaches brain tissue near the surface of the cortex. By combining data from these methods with advanced mathematical modelling, researchers created indicators that reflect how effectively the brain regulates blood flow and oxygen delivery in response to natural fluctuations in blood pressure and carbon dioxide levels.
Participants who scored higher on these indicators—meaning their brain blood vessels functioned more similarly to those of cognitively healthy individuals—showed lower levels of amyloid plaques and had larger hippocampal volumes. Both characteristics are widely recognised as signs of a lower risk of Alzheimer’s disease. Researchers also observed that individuals diagnosed with mild cognitive impairment or dementia tended to display weaker vascular indicators than cognitively healthy participants. This pattern supports the growing view that reduced cerebrovascular function may be part of the broader continuum of Alzheimer’s disease rather than simply a consequence of later-stage degeneration.
The researchers emphasise that these findings do not prove a direct cause-and-effect relationship. Instead, the study provides a snapshot showing that vascular health and established Alzheimer’s markers are closely linked. However, the techniques used in the research are less expensive and easier to perform than traditional brain imaging methods such as MRI or PET scans. Because they do not require injections, radiation, or demanding tasks from patients, they may eventually prove useful for large-scale screening or for individuals who cannot tolerate more intensive imaging procedures. Long-term studies are now underway to determine whether changes in these vascular signals can predict future cognitive decline or reveal whether improving vascular health might help slow Alzheimer’s-related brain changes.
More information: Amaryllis A. Tsiknia et al, Cerebrovascular regulation dynamics and Alzheimer’s neuroimaging phenotypes, Alzheimer’s and Dementia: The Journal of the Alzheimer’s Association. DOI: 10.1002/alz.71146
Journal information: Alzheimer’s and Dementia: The Journal of the Alzheimer’s Association Provided by Keck School of Medicine of USC
