The relationships between age, sex, and cerebrovascular reactivity to hypercapnia using traditional and kinetic-based analyses in healthy adults

Figures

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  Figure 1.. An example of MCAv trace for one participant at rest (120 s) and following onset of hypercapnia (time 0, denoted by dotted line). Residual plot is included below. Hypercapnic response characterized by a monoexponential model with a delay term shown by the solid black line. Time delay (TD) presents the time from the start of hypercapnia (0 s) to the onset of the exponential rise. Time constant (τ) presents the time taken to reach 63% of the response amplitude and it reflects the rate of increase in MCAv. Amplitude (Amp) presents the change from baseline to the peak of the exponential increase in MCAv. MCAv, middle cerebral artery velocity.

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  Figure 2.. A and B: linear regression analysis demonstrating the relationships between age and baseline middle cerebral artery velocity (MCAv; A) and cerebrovascular resistance index (CVRi; B; n = 73, females = 39). Solid line represents the regression fit for males, and dotted line represents the regression fit for female participants. Hierarchical regression models (P value and R2) are presented for the relationship with age (model 1), the relationship with sex (model 2), and the moderator relationship of the sex-dependent relationship with age (model 3). Slope coefficients (β) of the relationship with age are presented for males and females separately (model 3). MCAv, middle cerebral artery velocity.

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  Figure 3.. A and B: linear regression analysis demonstrating the relationships between age and CVR (n = 73, females = 39; A) and %ICA dilation and age (n = 58, females = 31; B). Solid line represents the regression fit for males, and dotted line represents the regression fit for female participants. Hierarchical regression models (P value and R2) are presented for the relationship with age (model 1), the relationship with sex (model 2), and the moderator relationship of the sex-dependent relationship with age (model 3). Slope coefficients (β) of the relationship with age are presented for males and females separately (model 3). CVR, cerebrovascular reactivity; ICA, internal carotid artery.

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  Figure 4.. A and B: linear regression analysis demonstrating the relationships between age and ICA percent change in mean blood flow (A) and ICA percent change in shear rate (n = 58, females = 31; B). Solid line represents the regression fit for males, and dotted line represents the regression fit for female participants. Hierarchical regression models (P value and R2) are presented for the relationship with age (model 1), the relationship with sex (model 2), and the moderator relationship of the sex-dependent relationship with age (model 3). Slope coefficients (β) of the relationship with age are presented for males and females separately (model 3). ICA, internal carotid artery.

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  Figure 5.. A and B: linear regression analysis demonstrating the relationships between age and MCAv time constant (τ; A) and PETCO2 time constant (n = 71, females = 38; B). Solid line represents the regression fit for males, and dotted line represents the regression fit for female participants. Hierarchical regression models (P value and R2) are presented for the relationship with age (model 1), the relationship with sex (model 2), and the moderator relationship of the sex-dependent relationship with age (model 3). Slope coefficients (β) of the relationship with age are presented for males and females separately (model 3). MCAv, middle cerebral artery velocity; PETCO2, end-tidal carbon dioxide.

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  Figure 6.. A and B: linear regression analysis demonstrating the relationships between age and PETCO2 amplitude (A) and MCAv amplitude (n = 71, females = 38; B). Solid line represents the regression fit for males, and dotted line represents the regression fit for female participants (). Hierarchical regression models (P value and R2) are presented for the relationship with age (model 1), the relationship with sex (model 2), and the moderator relationship of the sex-dependent relationship with age (model 3). Slope coefficients (β) of the relationship with age are presented for males and females separately (model 3). MCAv, middle cerebral artery velocity; PETCO2, end-tidal carbon dioxide.