Cerebral blood flow

Cerebral blood flow (CBF) is how much blood your brain gets per minute, measured in mL per 100 g of tissue per minute. Three systems regulate it: autoregulation, sensitivity to arterial CO₂, and 'neurovascular coupling'. Neurovascular coupling is the local matching of flow to activity. When neurons fire, they and nearby astrocytes release vasoactive agents (nitric oxide, prostaglandins, potassium). Those relax the small arteries and capillary pericytes, raising flow where the demand is. Resting CBF falls about 5% per decade. The drivers are rising vascular resistance, stiffer arteries, and weaker nitric-oxide production. Pulsatility rises after midlife and tracks with white-matter damage (Tarumi and Zhang, 2017). Chronic low flow (hypoperfusion) starves the brain of oxygen and glucose. It also stalls capillaries and worsens amyloid-β buildup. Worse clearance then deepens the vascular problem, a vicious cycle in Alzheimer's and vascular dementia (Toth et al., 2017). The good news: exercise helps. In a one-year trial (56 older adults), aerobic training raised CBF by about 5% versus 0% in controls (p = 0.007). It also cut vascular resistance 7% and tracked with better recall (Tomoto et al., 2023). A 2022 review found consistent links between exercise-driven CBF gains and cognition. But varied protocols limit the estimates (Renke et al., 2022). Flow is measured by arterial spin labeling MRI, transcranial Doppler, or phase-contrast MRI. Whether low flow causes dementia or just travels with it is still unresolved.

Last reviewed: June 22, 2026

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