The Effect of Age on the Elasticity of Human Iliac Arteries

Autopsy specimens of iliac arteries of 63 individuals of ages between birth and 91 years have been used to measure pressure–volume curves from which elastic diagrams, i.e. tension vs. elongation, and 'elastances' were deduced. For a smaller number of specimens, the longitudinal elastance was also measured. The resistance to deformation was also derived from the amount of excess pressure outside, which was required to empty the vessel (collapse pressure). The mean curves of tension vs. stretch for the different age groups showed a remarkable increase in resistance to stretch with age for both circumferential and longitudinal elastance. The incidence of atherosclerosis, shown by the independent grading of the histologist, increased with age, but vessels not showing atherosclerosis also showed a significant increase in 'elastance' with age. The thickness of the arterial wall was increased from birth to age 20 (about 3 times) but did not change significantly thereafter. There was a significant trend for the diameter of the lumen to decrease after age 30. This was not accounted for by intimal thickening, found in some specimens of greater age. Biophysical analysis in terms of the quantity of collagen fibers present in the wall suggests that not only does the quantity of collagenous material increase with age, but more importantly, the un-stretched length of these fibers decreases with age, as the 'slack' in them is taken up, possibly by cross-linkages or adhesions.