The impact of aging on cerebral vasomotor reactivity to carbon dioxide (1069.5)

The objective of this study was to determine the age‐related differences in cerebral vasomotor reactivity (CVMR) to carbon dioxide. Methods: 92 healthy adults aged 23‐77 underwent measurements of cerebral blood flow velocity (CBFV) using transcranial Doppler, mean arterial pressure, and end‐tidal CO 2 (EtCO 2 ) during baseline, hyperventilation (HVT), and modified rebreathing (RB). CVMR was determined by the maximal gain between changes in normalized CBFV (CBFV%) and EtCO 2 using a 3rd order polynomial model and its derivative. Results: Lower CBFV and EtCO 2 were related to increasing age at baseline. HVT decreased EtCO 2 by 21±4 mmHg while RB increased by 19±3 mmHg. Increasing age was related to smaller hypocapnic but larger hypercapnic changes in CBFV% at the end of HVT and RB, respectively. The maximal gain between CBFV% and EtCO 2 did not differ by age. Advanced age was associated with greater differences in EtCO 2 between the baseline and the level at which the maximum gain in CBFV% occurred. Conclusions: These findings suggest that age‐related reductions in baseline CBFV and EtCO 2 may lead to a decrease in hypocapnic but an increase in hypercapnic CBFV response. The larger differences in EtCO 2 between baseline and the maximal gain of CBFV% with aging may lead to blunted response of CBF to given changes in arterial CO 2 at levels close to baseline. Grant Funding Source : Supported by National Institute on Aging