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Effects of aging on the association between cerebrovascular responses to visual stimulation, hypercapnia and arterial stiffness.

Flück D, Beaudin AE, Steinback CD, Kumarpillai G, Shobha N, McCreary CR, Peca S, Smith EE, Poulin MJ - Front Physiol (2014)

Bottom Line: Aging is associated with decreased vascular compliance and diminished neurovascular- and hypercapnia-evoked cerebral blood flow (CBF) responses.In conclusion, older subjects had reduced neurovascular- and hypercapnia-mediated CBF responses.These findings suggest the reduced hypercapnia-evoked CBF responses through the MCA, in older individuals may be secondary to vascular stiffening.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Institute of Human Movement Sciences and Sport, ETH Zurich Zurich, Switzerland ; Department of Physiology and Pharmacology, Faculty of Medicine, University of Calgary Calgary, AB, Canada.

ABSTRACT
Aging is associated with decreased vascular compliance and diminished neurovascular- and hypercapnia-evoked cerebral blood flow (CBF) responses. However, the interplay between arterial stiffness and reduced CBF responses is poorly understood. It was hypothesized that increased cerebral arterial stiffness is associated with reduced evoked responses to both, a flashing checkerboard visual stimulation (i.e., neurovascular coupling), and hypercapnia. To test this hypothesis, 20 older (64 ± 8 year; mean ± SD) and 10 young (30 ± 5 year) subjects underwent a visual stimulation (VS) and a hypercapnic test. Blood velocity through the posterior (PCA) and middle cerebral (MCA) arteries was measured concurrently using transcranial Doppler ultrasound (TCD). Cerebral and systemic vascular stiffness were calculated from the cerebral blood velocity and systemic blood pressure waveforms, respectively. Cerebrovascular (MCA: young = 76 ± 15%, older = 98 ± 19%, p = 0.004; PCA: young = 80 ± 16%, older = 106 ± 17%, p < 0.001) and systemic (young = 59 ± 9% and older = 80 ± 9%, p < 0.001) augmentation indices (AI) were higher in the older group. CBF responses to VS (PCA: p < 0.026) and hypercapnia (PCA: p = 0.018; MCA: p = 0.042) were lower in the older group. A curvilinear model fitted to cerebral AI and age showed AI increases until ~60 years of age, after which the increase levels off (PCA: R (2) = 0.45, p < 0.001; MCA: R (2) = 0.31, p < 0.001). Finally, MCA, but not PCA, hypercapnic reactivity was inversely related to cerebral AI (MCA: R (2) = 0.28, p = 0.002; PCA: R (2) = 0.10, p = 0.104). A similar inverse relationship was not observed with the PCA blood flow response to VS (R (2) = 0.06, p = 0.174). In conclusion, older subjects had reduced neurovascular- and hypercapnia-mediated CBF responses. Furthermore, lower hypercapnia-mediated blood flow responses through the MCA were associated with increased vascular stiffness. These findings suggest the reduced hypercapnia-evoked CBF responses through the MCA, in older individuals may be secondary to vascular stiffening.

No MeSH data available.


Related in: MedlinePlus

Relationships between the cerebral augmentation index (Cerebral AI) and Systemic AI in the middle (MCA) and posterior cerebral arteries (PCA) (A) and Cerebral AI and Age in MCA and PCA (B).
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Figure 5: Relationships between the cerebral augmentation index (Cerebral AI) and Systemic AI in the middle (MCA) and posterior cerebral arteries (PCA) (A) and Cerebral AI and Age in MCA and PCA (B).

Mentions: Cerebral AI for both the PCA and the MCA was highly correlated (p < 0.001) with systemic AI (Figure 5A). Furthermore, the curvilinear model fitted to the cerebral AI and age relationship was significant for both arteries (p < 0.001; Figure 5B). Figure 6 shows the relationships between responses in PCA Vmean to the visual stimulation and cerebral AI as well as the relationships between PCA and MCA hypercapnia reactivities and cerebral AI. The change in PCA Vmean (relative and absolute) in response to the visual stimulation was not related cerebral AI (p ≥ 0.128). Similarly, the correlations between absolute, and relative, PCA hypercapnia reactivity and cerebral AI were not significant (p ≥ 103). In contrast, there was a significant negative correlation between relative, and absolute, measures of MCA hypercapnia reactivities and cerebral AI (p ≤ 0.013) with lower reactivity at higher cerebral AIs.


Effects of aging on the association between cerebrovascular responses to visual stimulation, hypercapnia and arterial stiffness.

Flück D, Beaudin AE, Steinback CD, Kumarpillai G, Shobha N, McCreary CR, Peca S, Smith EE, Poulin MJ - Front Physiol (2014)

Relationships between the cerebral augmentation index (Cerebral AI) and Systemic AI in the middle (MCA) and posterior cerebral arteries (PCA) (A) and Cerebral AI and Age in MCA and PCA (B).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3928624&req=5

Figure 5: Relationships between the cerebral augmentation index (Cerebral AI) and Systemic AI in the middle (MCA) and posterior cerebral arteries (PCA) (A) and Cerebral AI and Age in MCA and PCA (B).
Mentions: Cerebral AI for both the PCA and the MCA was highly correlated (p < 0.001) with systemic AI (Figure 5A). Furthermore, the curvilinear model fitted to the cerebral AI and age relationship was significant for both arteries (p < 0.001; Figure 5B). Figure 6 shows the relationships between responses in PCA Vmean to the visual stimulation and cerebral AI as well as the relationships between PCA and MCA hypercapnia reactivities and cerebral AI. The change in PCA Vmean (relative and absolute) in response to the visual stimulation was not related cerebral AI (p ≥ 0.128). Similarly, the correlations between absolute, and relative, PCA hypercapnia reactivity and cerebral AI were not significant (p ≥ 103). In contrast, there was a significant negative correlation between relative, and absolute, measures of MCA hypercapnia reactivities and cerebral AI (p ≤ 0.013) with lower reactivity at higher cerebral AIs.

Bottom Line: Aging is associated with decreased vascular compliance and diminished neurovascular- and hypercapnia-evoked cerebral blood flow (CBF) responses.In conclusion, older subjects had reduced neurovascular- and hypercapnia-mediated CBF responses.These findings suggest the reduced hypercapnia-evoked CBF responses through the MCA, in older individuals may be secondary to vascular stiffening.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Institute of Human Movement Sciences and Sport, ETH Zurich Zurich, Switzerland ; Department of Physiology and Pharmacology, Faculty of Medicine, University of Calgary Calgary, AB, Canada.

ABSTRACT
Aging is associated with decreased vascular compliance and diminished neurovascular- and hypercapnia-evoked cerebral blood flow (CBF) responses. However, the interplay between arterial stiffness and reduced CBF responses is poorly understood. It was hypothesized that increased cerebral arterial stiffness is associated with reduced evoked responses to both, a flashing checkerboard visual stimulation (i.e., neurovascular coupling), and hypercapnia. To test this hypothesis, 20 older (64 ± 8 year; mean ± SD) and 10 young (30 ± 5 year) subjects underwent a visual stimulation (VS) and a hypercapnic test. Blood velocity through the posterior (PCA) and middle cerebral (MCA) arteries was measured concurrently using transcranial Doppler ultrasound (TCD). Cerebral and systemic vascular stiffness were calculated from the cerebral blood velocity and systemic blood pressure waveforms, respectively. Cerebrovascular (MCA: young = 76 ± 15%, older = 98 ± 19%, p = 0.004; PCA: young = 80 ± 16%, older = 106 ± 17%, p < 0.001) and systemic (young = 59 ± 9% and older = 80 ± 9%, p < 0.001) augmentation indices (AI) were higher in the older group. CBF responses to VS (PCA: p < 0.026) and hypercapnia (PCA: p = 0.018; MCA: p = 0.042) were lower in the older group. A curvilinear model fitted to cerebral AI and age showed AI increases until ~60 years of age, after which the increase levels off (PCA: R (2) = 0.45, p < 0.001; MCA: R (2) = 0.31, p < 0.001). Finally, MCA, but not PCA, hypercapnic reactivity was inversely related to cerebral AI (MCA: R (2) = 0.28, p = 0.002; PCA: R (2) = 0.10, p = 0.104). A similar inverse relationship was not observed with the PCA blood flow response to VS (R (2) = 0.06, p = 0.174). In conclusion, older subjects had reduced neurovascular- and hypercapnia-mediated CBF responses. Furthermore, lower hypercapnia-mediated blood flow responses through the MCA were associated with increased vascular stiffness. These findings suggest the reduced hypercapnia-evoked CBF responses through the MCA, in older individuals may be secondary to vascular stiffening.

No MeSH data available.


Related in: MedlinePlus