5.4 Age-Induced Increase in the Energy Transmitted Towards the Cerebral Circulation as a Contributor to Impaired Brain Function

Abstract

Background and Aims

The increase in arterial stiffness and pressure pulsatility with age is identified as a key contributor to cognitive impairment; nevertheless, the underlying hemodynamic mechanisms remain unclear. A hypothesis, proposed by (1), suggests that the preferential stiffening of the central arteries as compared to the periphery changes the impedance distribution of the arterial network and exposes the cerebral circulation to the deleterious effects of excessive pulsatile energy. The aim of the present study was to test this hypothesis using a previously developed mathematical model of the ageing cardiovascular system (2).

Methods

For each decade of age, forward and backward components of wave and hydraulic power and energy were calculated (3) at the ascending aorta as well as at the cerebral blood supply vessels, i.e. the vertebral and internal carotid arteries. Subsequently, we isolated the component of hydraulic energy (HE) related to the initial forward compression wave (FCW) by restricting the analysis to early systole (0–0.2 sec) and calculated the respective energy transmission coefficients.

Results

Ageing was associated with an increase in proximal aortic FCW wave power (dictated by the augmented ventricular contractility) and a slight increase in total hydraulic energy. The FCW energy transmission coefficients were almost doubled for all brain vessels as shown in Fig. 1.

Conclusion

Our findings support the hypothesis that age-related central arterial stiffening leads to an enhanced energy transmission of the early systolic forward wave towards brain vessels, potentially contributing to impaired brain function with increasing age.