Abstract

Ageing reduces cerebral blood flow (CBF), while mean arterial pressure (MAP) becomes elevated. According to 'the selfish brain' hypothesis of hypertension, a reduction in vertebral artery blood flow (VA) leads to increased sympathetic activity and thus increases MAP. In twenty-two young (24±3years; mean±SD) and eleven elderly (70±5years) normotensive men, duplex ultrasound evaluated whether the age-related reduction in CBF affects VA more than internal carotid artery (ICA) blood flow. Pulse-contour analysis evaluated MAP while near-infrared spectroscopy determined frontal lobe oxygenation and transcranial Doppler middle cerebral artery mean blood velocity (MCA Vmean ). During supine rest, MAP (90±13 versus 78±9mmHg; P<0·001) was elevated in the older subjects while their frontal lobe oxygenation (68±7% versus 77±7%; P<0·001), MCA Vmean (49±9 versus 60±12cm s-1 ; P=0·016) and CBF (754±112 versus 900±144mlmin-1 ; P=0·004) were low reflected in VA (138±48 versus 219±50mlmin-1 ; P<0·001) rather than in ICA flow (616±96 versus 680±120mlmin-1 ; P=0·099). In conclusion, blood supply to the brain and its oxygenation are affected by ageing and the age-related decline in VA flow appears to be four times as large as that in ICA and could be important for the age-related increase in MAP.

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