The effect of age on the renin-angiotensin-aldosterone systems and other physiological variables in normal subjects

The influence of age on the renin-angiotensin-aldosterone (RAA) system in 125 normal subjects, ages ranging from 13-90, in Valencia, Venezuela, was evaluated. The subjects selected were tested during their normal life style, on their usual sodium and potassium diet. Their RAA system was stimulated by walking for 2-3 hours. A highly significant inverse correlation was found between age and stimulated plasma renin activity (r = -0.7149, p less than 0.001), and between age and urinary aldosterone (r = 0.4837, p less than 0.001). No significant correlation between age and serum aldosterone was found. The most significant changes in levels of these hormones were found between ages 55 and 60 when renin and aldosterone values decreased markedly. This decrease accelerates with increasing age. Plasma renin presented an appreciable percentage of decrease when compared to the highest levels found in the lowest age group; plasma renin decreased 80%, while urinary aldosterone decreased only 40% between ages 80 and 90. In the over-60 groups this relationship between plasma renin activity and urinary and serum aldosterone levels showed both aldosterone values were higher than the corresponding plasma renin levels. We have no clear explanation for the "physiologicalhyperaldosteronism" found in groups over age 60. Age is an indispensible consideration in normal RAA system values. More intensive studies of over age 60 subjects are necessary.