The effect of age on the distensibility of the abdominal aorta of man.

The variation with age in distensibility and the dimensions of the abdominal aorta at the bifurcation have been measured in 43 fresh human cadavers. The age range was from birth to 69 years, both sexes being represented. Patients with vascular disease were excluded. Barium sulfate infused into the aorta through an iliac artery enabled the change in diameter to be measured from a roentgenogram with change in pressure. Incremental strain value could thus be calculated. Strain value increased from 0.02 at birth to a maximum at the end of the first decade of life and then decreased to less than 0.01 by the age of 70 years. Aortas in the age group of four to 11 years showed less stiffness with increasing pressure than at other ages. Variations of strain with age correlate with alterations in the ratio of aortic wall collagen to elastin in the young. An increase in the thickness of the wall and an atheroma, in response to prolonged hemodynamic stress, account for increased stiffness in the older age groups. Other age and disease factors may play a part, but further work is required in man to examine the role of relative wall thickness, elastic modulus and alteration in wall structure in determining the variation of aortic distensibility with age reported herein.