The age-related reduction in cerebral blood flow affects vertebral artery more than internal carotid artery blood flow

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 +/- 3 years; mean +/- SD) and eleven elderly (70 +/- 5 years) 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 V-mean). During supine rest, MAP (90 +/- 13 versus 78 +/- 9 mmHg; P<0 center dot 001) was elevated in the older subjects while their frontal lobe oxygenation (68 +/- 7% versus 77 +/- 7%; P<0 center dot 001), MCA V-mean (49 +/- 9 versus 60 +/- 12 cm s(-1); P = 0 center dot 016) and CBF (754 +/- 112 versus 900 +/- 144 ml min(-1); P = 0 center dot 004) were low reflected in VA (138 +/- 48 versus 219 +/- 50 ml min(-1); P<0 center dot 001) rather than in ICA flow (616 +/- 96 versus 680 +/- 120 ml min(-1); P = 0 center dot 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.