RENAL-FUNCTION IN THE ELDERLY - IMPACT OF HYPERTENSION AND CARDIAC-FUNCTION

In senescence renal function is thought to decline markedly even in th e absence of renal disease. It has also been proposed that the changes in renal function with age are not uniform and that confounding facto rs such as hypertension or atherosclerosis may play a role. We perform ed a comprehensive study to compare several aspects of renal function in four groups: (i) young healthy normotensive subjects (N = 24; 13 ma les; mean age 26 +/- 3 years); (ii) elderly healthy normotensive subje cts (elderly NT; N = 29; 13 males; 68 +/- 7 years); (iii) elderly trea ted and untreated hypertensive patients (elderly HT; N = 25; 13 males; 70 +/- 6 years); and (iv) elderly patients with compensated mild to m oderate heart failure (elderly HF; N = 14; 6 males; 69 +/- 6 years). C ompared to young subjects mean GFR (C-In) and ERPF (C-PAH) were signif icantly lower in the elderly, despite similar mean plasma creatinine l evels (young, 121 +/- 11, 650 +/- 85 ml/min/1.73 m(2); elderly NT, 103 +/- 11, 486 +/- 102; elderly HT, 103 +/- 13, 427 +/- 55; elderly HF, 92 +/- 14, 377 +/- 103). Nevertheless, GFR was within the normal range in the majority of elderly NT and HT, but not in elderly HF. ERPF was significantly lower in elderly HT as compared with elderly NT, and st ill lower in elderly HF. Mean renovascular resistance and filtration f raction were significantly higher in the elderly, particularly in elde rly HT and KF as compared with the young. Mean fractional excretion of Na+ was similar in all groups studied, but the lithium clearance was significantly lower in the elderly, suggesting a greater proximal and less distal sodium reabsorption in senescence. In the elderly, mean PT H concentration and urinary excretion of pyridoline cross-links were s ignificantly higher and mean 25-(OH)D-3, calcitriol and phosphate conc entrations significantly lower; the correlation between PTH and GFR wa s significant (r = -0.432, P < 0.001). The results document that the d ecrease in renal hemodynamics with senescence is less marked than sugg ested by some studies using less stringent methodology and inclusion c riteria. Comorbid conditions confound renal function in the elderly. A ge-associated changes in renal hemodynamics are accompanied by signifi cant alterations of renal hormones and of renal sodium handling.