Effects of aging per se on arterial stiffness: systemic and regional compliance in beagles

Although previous studies have suggested that aging results in an increase in vascular stiffness, diseases that increase in prevalence with advanced age may have confounded the results of some of this past research. The purpose of this investigation was to determine whether aging per se results in reduced arterial compliance by using animals that are resistant to atherosclerosis and do not develop hypertension or hyperlipidemias with advanced age. We evaluated systemic and regional (femoral) arterial compliance in older (110 +/- 8 months old) and in younger (27 +/- 2 months old) female beagle dogs by using a computer-based assessment of the diastolic decay of arterial pressure waveforms and a modified Windkessel model of the circulation. Although systemic arterial pressure was very similar in both age groups, cardiac output was 29% lower (p = 0.03) and systemic vascular resistance was 24% higher (p = 0.02) in the older dogs. Moreover, there was an age-related reduction in systemic arterial compliance, derived both from the exponential decay in the arterial pulse (C1) (p = 0.05) and that derived from the oscillatory component of the diastolic pulse wave (C2) (p = 0.04). By contrast, although femoral vascular resistance was 25% higher in the older dogs (p = 0.04), regional (femoral) vascular compliance measured after femoral arterial occlusion was also 25% reduced but was not significantly changed with age (p = 0.14). These results demonstrate that systemic arterial compliance is reduced with age in dogs, extending this finding to animals without age-related diseases that frequently occur in older human beings. Regional compliance, evaluated in the isolated femoral vascular bed, also tends to be reduced with age, but variability in this parameter in dogs reduces the significance of this finding.