Effects of aging on the cerebrovascular orthostatic response.

When healthy subjects stand up, it is associated with a reduction in cerebral blood velocity and oxygenation although cerebral autoregulation would be considered to prevent a decrease in cerebral perfusion. Aging is associated with a higher incidence of falls, and in the elderly falls may occur particularly during the adaptation to postural change. This study evaluated the cerebrovascular adaptation to postural change in 15 healthy younger (YNG) vs. 15 older (OLD) subjects by recordings of the near-infrared spectroscopy-determined cerebral oxygenation (cO₂Hb) and the transcranial Doppler-determined mean middle cerebral artery blood velocity (MCA V(mean)). In OLD (59 (52-65) years) vs. YNG (29 (27-33) years), the initial postural decline in mean arterial pressure (-52 ± 3% vs. -67 ± 3%), cO₂Hb (-3.4 ± 2.5 μmoll(-1) vs. -5.3 ± 1.7 μmoll(-1)) and MCA V(mean) (-16 ± 4% vs. -29 ± 3%) was smaller. The decline in MCA V(mean) was related to the reduction in MAP. During prolonged orthostatic stress, the decline in MCA V(mean)and cO(2)Hb in OLD remained smaller. We conclude that with healthy aging the postural reduction in cerebral perfusion becomes less prominent.