Cerebral oxygenation declines in healthy elderly subjects in response to assuming the upright position

Background and Purpose-With increasing age, assuming the upright position i s more often accompanied by symptoms such as dizziness and lightheadedness, possibly as a result of a diminished oxygen supply to the brain due to imp aired cerebral autoregulation. We aimed to quantify postural changes in cer ebral oxygenation and systemic hemodynamics in healthy elderly and young su bjects. Methods-In 18 healthy elderly subjects (aged 70 to 83 years) and 10 healthy young subjects (aged 22 to 45 years), frontal cortical oxygenation and hem odynamic responses were continuously monitored by near infrared spectroscop y and Finapres, respectively, before and during 10 minutes of active standi ng. Results-Cortical oxyhemoglobin concentration [O(2)Hb] decreased by -4.6+/-2 2 mu mol/L (P<0.001) and cortical deoxyhemoglobin concentration increased b y 1.5+/-2.4 mu mol/L (P<0.05) in the elderly subjects after posture change, whereas these variables did not change significantly in the young subjects . The postural hemodynamic changes tended to be attenuated in the elderly s ubjects, except for the increases in systolic blood pressure (BP). Smaller postural increases in diastolic BP were related to larger [O(2)Hb] decrease s (r=0.53, P<0.01, corrected for the age effect). Conclusions-Assuming the upright position evokes an asymptomatic decrease i n frontal cortical oxygenation in healthy elderly subjects but not in healt hy young subjects. Cortical [O(2)Hb] changes are affected by diastolic BP c hanges. These findings may indicate that regulation of cerebral oxygenation alters with increasing age.