1 NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal, Montreal, QC, Canada.
2 Centre de recherche de l'Institut Universitaire de Gériatrie de Montréal (CRIUGM), Montreal, QC, Canada.
3 Department of Neurosciences, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada.
4 Groupe de Recherche sur le Système Nerveux Central (GRSNC), Université de Montréal, Montreal, QC, Canada.
5 Centre interdisciplinaire de recherche sur le cerveau et l'apprentissage (CIRCA), Université de Montréal, Montreal, QC, Canada.
6 Department of Biomedical Sciences, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada.
7 Montreal Heart Institute, Montreal, QC, Canada.
8 PERFORM Centre, Concordia University, Montreal, QC, Canada.
9 Department of Psychology, Faculty of Arts and Sciences, Université de Montréal, Montreal, QC, Canada.
10 Department of Medicine, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada.
11 Institut de Recherches Cliniques de Montréal, Université de Montréal, Montreal, QC, Canada.
12 Physics Department, Concordia University, Montreal, QC, Canada.
13 Functional Neuroimaging Unit, Centre de recherche de l'Institut Universitaire de Gériatrie de Montréal (CRIUGM), Université de Montréal, Montreal, QC, Canada.
14 Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada.

Background: Vascular risk factors such as arterial stiffness play an important role in the etiology of Alzheimer's disease (AD), presumably due to the emergence of white matter lesions. However, the impact of arterial stiffness to white matter structure involved in the etiology of AD, including the corpus callosum remains poorly understood.

Objective: The aims of the study are to better understand the relationship between arterial stiffness, white matter microstructure, and perfusion of the corpus callosum in older adults.

Methods: Arterial stiffness was estimated using the gold standard measure of carotid-femoral pulse wave velocity (cfPWV). Cognitive performance was evaluated with the Trail Making Test part B-A. Neurite orientation dispersion and density imaging was used to obtain microstructural information such as neurite density and extracellular water diffusion. The cerebral blood flow was estimated using arterial spin labelling.

Results: cfPWV better predicts the microstructural integrity of the corpus callosum when compared with other index of vascular aging (the augmentation index, the systolic blood pressure, and the pulse pressure). In particular, significant associations were found between the cfPWV, an alteration of the extracellular water diffusion, and a neuronal density increase in the body of the corpus callosum which was also correlated with the performance in cognitive flexibility.

Conclusion: Our results suggest that arterial stiffness is associated with an alteration of brain integrity which impacts cognitive function in older adults.