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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

Absolute (cm/s) and relative (%) changes (Δ) in posterior (PCA) and middle cerebral artery (MCA) blood velocity (A) and cerebrovascular conductance (B) in response to euoxic hypercapnic test.P-values provided for comparison between young and older volunteers.
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Figure 3: Absolute (cm/s) and relative (%) changes (Δ) in posterior (PCA) and middle cerebral artery (MCA) blood velocity (A) and cerebrovascular conductance (B) in response to euoxic hypercapnic test.P-values provided for comparison between young and older volunteers.

Mentions: Absolute and relative increases in PCA and MCA Vmean, and CVC with hypercapnia are shown in Figure 3. There was a significant interaction between the Hypercapnic Stages and Age Groups main effects for both PCA (p = 0.004) and MCA (p < 0.001) Vmean. In addition, the interaction between the Hypercapnic Stages and Age Groups was significant for CVC in both arteries (PCA: p = 0.039; MCA: p = 0.007). Post-hoc comparisons showed the absolute, and relative, increases in PCA Vmean were significantly lower in older subjects (p ≤ 0.031) while the absolute increase in MCA Vmean was lower in the older subjects (p ≤ 0.001) and the relative increase in MCA Vmean showed a trend to be lower in the older group (p = 0.097). Also, the absolute increase in CVC with hypercapnia was lower in the older group for both the PCA (p = 0.025), and MCA (p = 0.005), but the relative increase in CVC showed only a trend to be lower in the older group for the PCA (p = 0.057) while MCA CVC was similar between the two groups (p = 0.237). The interaction between the Hypercapnic Stages and Age Groups main effects was significant for PCA and MCA Vdia (p ≤ 0.001) and Vrefl (p ≤ 0.024), but not Vsys (p ≥ 0.068). Table 2 shows the results of post-hoc age group comparisons of the change in PCA and MCA Vdia, Vsys, and Vrefl with hypercapnia.


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)

Absolute (cm/s) and relative (%) changes (Δ) in posterior (PCA) and middle cerebral artery (MCA) blood velocity (A) and cerebrovascular conductance (B) in response to euoxic hypercapnic test.P-values provided for comparison between young and older volunteers.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 3: Absolute (cm/s) and relative (%) changes (Δ) in posterior (PCA) and middle cerebral artery (MCA) blood velocity (A) and cerebrovascular conductance (B) in response to euoxic hypercapnic test.P-values provided for comparison between young and older volunteers.
Mentions: Absolute and relative increases in PCA and MCA Vmean, and CVC with hypercapnia are shown in Figure 3. There was a significant interaction between the Hypercapnic Stages and Age Groups main effects for both PCA (p = 0.004) and MCA (p < 0.001) Vmean. In addition, the interaction between the Hypercapnic Stages and Age Groups was significant for CVC in both arteries (PCA: p = 0.039; MCA: p = 0.007). Post-hoc comparisons showed the absolute, and relative, increases in PCA Vmean were significantly lower in older subjects (p ≤ 0.031) while the absolute increase in MCA Vmean was lower in the older subjects (p ≤ 0.001) and the relative increase in MCA Vmean showed a trend to be lower in the older group (p = 0.097). Also, the absolute increase in CVC with hypercapnia was lower in the older group for both the PCA (p = 0.025), and MCA (p = 0.005), but the relative increase in CVC showed only a trend to be lower in the older group for the PCA (p = 0.057) while MCA CVC was similar between the two groups (p = 0.237). The interaction between the Hypercapnic Stages and Age Groups main effects was significant for PCA and MCA Vdia (p ≤ 0.001) and Vrefl (p ≤ 0.024), but not Vsys (p ≥ 0.068). Table 2 shows the results of post-hoc age group comparisons of the change in PCA and MCA Vdia, Vsys, and Vrefl with hypercapnia.

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