Journal
JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM
Volume 37, Issue 1, Pages 344-355Publisher
SAGE PUBLICATIONS INC
DOI: 10.1177/0271678X15626156
Keywords
Middle cerebral artery; cerebrovascular control; transcranial Doppler ultrasound; aging
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Funding
- Canadian Institutes for Health Research (CIHR) Team Grant Physical Activity, Mobility, and Neural Health'' [217532]
- CIHR
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This study quantified the effect of age on cerebrovascular reactivity and cerebrovascular conductance while accounting for differences in grey matter volume in younger (YA: n = 12; 24 +/- 4 years, six females) and older adults (OA: n = 10; 66 +/- 7 years; five females). Cerebral blood flow velocity (CBFV; transcranial Doppler) in the middle cerebral artery (MCA), MCA cross-sectional area (CSA), intracranial volumes (magnetic resonance imaging), and mean arterial pressure (MAP; Finometer), were measured under normocapnic and hypercapnic (6% carbon dioxide) conditions. Cerebral blood flow (CBF) was quantified from CBFV and MCA CSA and normalized to grey matter volume. Grey matter volume was 719 +/- 98 mL in YA and 622 +/- 50 mL in OA (P = 0.009). Cerebrovascular reactivity (%Delta CBF/Delta PETCO2) was not different between YA and OA. In contrast, cerebrovascular conductance (CBF/MAP) in response to hypercapnia was reduced in OA (P = 0.02). Of note, MAP increased more with hypercapnia in OA compared with YA. Therefore, the central hemodynamic response to hypercapnia compensated for a diminished dilatory response downstream from the MCA so that the CBF response to hypercapnia per unit of brain mass was not affected by age. This impairment was not detected by traditional measures of cerebrovascular reactivity.
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