Aging and sodium homeostasis.

Deterioration of glomerular filtration rate appears to be progressive throughout life whereas sodium intake tends to remain constant. The influence of aging may be amplified by intrinsic renal disease, unilateral nephrectomy or renovascular abnormalities. Changes in the tubular reabsorption of sodium will allow the excretory capacity of the kidney to adjust to fluctuations in normal sodium intake. However, restriction of dietary sodium may be associated with a sluggish renal response; a sodium wasting state that could lead to significant deterioration in renal function and orthostatic hypotension, may occur. Conversely, increasing dietary sodium in older subjects may result in a rise in arterial pressure more often than in younger subjects. Dietary sodium restriction should be carefully controlled in elderly subjects.