Chronic physical activity mitigates cerebral hypoperfusion during central hypovolemia in elderly humans

Kevin Formes, Peizhen Zhang, Nancy Tierney, Frederick Schaller, Xiangrong Shi

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Abstract

This study sought to test the hypothesis that orthostasis-induced cerebral hypoperfusion would be less severe in physically active elderly humans (ACT group) than in sedentary elderly humans (SED group). The peak O2 uptake of 10 SED (67.1 ± 1.4 yr) and 9 ACT (68.0 ± 1.1 yr) volunteers was determined by a graded cycling exercise test (22.1 ± 1.2 vs 35.8 ± 1.3 ml•min-1•kg-1, P < 0.01). Baseline mean arterial pressure (MAP; tonometry) and middle cerebral arterial blood flow velocity (VMCA; transcranial Doppler) were similar between the groups (SED vs. ACT group: 91 ± 3 vs. 87 ± 3 mmHg and 54.9 ± 2.3 vs. 57.8 ± 3.2 cm/s, respectively), whereas heart rate was higher and stroke volume (bioimpedance) was smaller in the SED group than in the ACT group. Central hypovolemia during graded lower body negative pressure (LBNP) was larger (P < 0.01) in the ACT group than in the SED group. However, the slope of VMCA/LBNP was smaller (P < 0.05) in the ACT group (0.159 ± 0.016 cm/s/Torr) than in the SED group (0.211 ± 0.008 cm/s/Torr). During LBNP, the SED group had a greater augmentation of cerebral vasomotor tone (P < 0.05) and hypocapnia (P < 0.001) compared with the ACT group. Baseline MAP variability and VMCA variability were significantly smaller in the SED group than in the ACT group, i.e., 0.49 ± 0.07 vs. 1.04 ± 0.16 (mmHg)2 and 1.06 ± 0.19 vs. 4.24 ± 1.59 (cm/s)2, respectively. However, transfer function gain, coherence, and phase between MAP and VMCA signals (Welch spectral estimator) from 0.08-0.18 Hz were not different between SED (1.41 ± 0.18 cm•s-1•mmHg-1, 0.63 ± 0.06 units, and 38.03 ± 6.57° ) and ACT (1.65 ± 0.44 cm•s -1•mmHg-1, 0.56 ± 0.05 units, and 48.55 ± 11.84° ) groups. We conclude that a physically active lifestyle improves the intrinsic mechanism of cerebral autoregulation and helps mitigate cerebral hypoperfusion during central hypovolemia in healthy elderly adults.

Original languageEnglish
Pages (from-to)H1029-H1037
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume298
Issue number3
DOIs
Publication statusPublished - 1 Mar 2010

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Keywords

  • Cerebral vasomotor tone
  • Hypocapnia
  • Lower body negative pressure
  • Transfer function gain

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