Carotid arterial stiffness and cerebral blood flow in amnestic mild cognitive impairment

Background: Central arterial stiffness is an emerging risk factor of age-related cognitive impairment and Alzheimer’s disease (AD). However, the underlying pathophysiological mechanisms remain unclear. Objective: We tested the hypothesis that carotid arterial stiffness is associated with reduced cerebral blood flow (CBF) and increased cerebrovascular resistance (CVR) in patients with amnestic mild cognitive impairment (MCI), a prodromal stage of AD. Methods: Fifty-four patients with amnestic MCI and 24 cognitively normal subjects (CN) of similar age and sex to MCI patients underwent measurements of CBF and carotid β-stiffness index using ultra-sonography and applanation tonometry. Total CBF was measured as the sum of CBF from both the internal carotid and vertebral arteries, and divided by total brain tissue mass (assessed with MRI) to obtain normalized CBF (nCBF). Results: Relative to CN subjects, MCI patients showed lower nCBF (53.3 ± 3.2 vs 50.4±3.4 mL/100 g/min, P < 0.001) and higher CVR (0.143 ± 0.019 vs 0.156 ± 0.023 mmHg/mL/min, P < 0.015). Multiple linear regression analysis showed that nCBF was negatively associated with carotid β-stiffness index (B =-0.822, P < 0.001); CVR was positively associated with carotid systolic pressure (B = 0.001, P < 0.001) after adjustment for age, sex, body mass index, and MCI status. Conclusion: These findings suggest that carotid artery stiffening may contribute at least in part to the reduced nCBF and increased CVR in patients with MCI associated with augmented carotid arterial pulsatility.