Stiff arteries, silent brain changes; a new diagnostic tool in Alzheimer's disease pathology

Arterial stiffening refers to the reduced ability of an artery to contract or expand in response to fluctuations in pressure [1]. Arterial stiffening is associated with dementia-related pathology, such as microbleeds, white matter hyperintensities and deposition of the dementia-related plaque; Aβ1–40[2]. Arterial stiffening, therefore, likely plays a role in Alzheimer's disease pathogenesis. Zimmerman et al. aimed to explore the relationship between critical arterial stiffening parameters and early metabolic alterations in the brain. The authors included 67 cognitively normal adults, aged between 27 and 88 years and categorized into three distinct age groups: young, middle-aged, and older adults. Participants underwent F-fluorodeoxyglucose PET (F-FDG PET) imaging to evaluate brain metabolism; in conjunction with assessments of arterial stiffening, such as pulse wave velocity (PWV) and the time-to-peak of the reflected backward carotid pulse wave (bT). The authors focused on how these vascular factors related to brain metabolism, particularly in brain regions known to be affected by Alzheimer's disease. The study found that an indication of an earlier return of the reflected arterial pressure wave (bT) was significantly associated with a reduction in brain metabolism in areas of the brain vulnerable to Alzheimer's disease; this finding was irrespective of the patients’ ages. Using voxel-based analysis, the authors further identified 40 distinct brain clusters, including key regions such as the posterior cingulate and precuneus regions, where a decreased bT correlated with lower glucose metabolism. These regions are known to show early alterations linked to Alzheimer's disease [3], highlighting the significance of this vascular marker. One of the key strengths of Zimmerman et al. s findings are the robustness of the results, remaining significant after adjusting for other cardiovascular risk factors, such as heart rate and blood pressure. The association between shorter bT and hypometabolism in brain regions vulnerable to Alzheimer's disease pathogenesis was consistent across all groups, suggesting that vascular health, as reflected by this measure, may influence brain health well before cognitive decline becomes apparent. The study's findings are exciting because they emphasize the potential of bT as a noninvasive, early biomarker, to evaluate the risk of Alzheimer's disease. The importance of Zimmerman et al. s findings are two-fold, firstly, they emphasize that arterial stiffening is not merely a by-product of ageing, but instead that arterial stiffening plays a vital role in brain health and the development of Alzheimer's disease. Secondly, the emphasis on the timing of the reflected arterial wave introduces a fresh perspective on how vascular dynamics may influence the progression of Alzheimer's disease. Although earlier research has established a connection between overall cardiovascular health and cognitive decline [4], the authors specifically identify the early return of the arterial pressure wave as a distinct predictor of diminished brain metabolism in areas associated with Alzheimer's disease. The implications of this research for the early detection and prevention of Alzheimer's disease are very encouraging. Given that bT can be easily measured using noninvasive methods such as application tonometry [5], it has the potential to be incorporated into clinical practice to identify individuals at an elevated risk of Alzheimer's disease, well before the onset of symptoms. This presents a significant opportunity for early intervention strategies, which may include lifestyle changes or therapies designed to enhance vascular health, thereby potentially delaying or preventing the onset of Alzheimer's disease [6]. In summary, Zimmerman et al. present compelling evidence that an early return of the reflected arterial wave serves as a crucial indicator of initial brain metabolic decline in regions susceptible to Alzheimer's disease. The capacity to detect these alterations through straightforward, noninvasive, vascular assessments could revolutionize the approach to early diagnosis of Alzheimer's disease; redirecting attention towards vascular health as a fundamental factor in brain ageing and neurodegenerative disease. ACKNOWLEDGEMENTS Conflicts of interest There are no conflicts of interest.