Relation of nocturnal polyuria of the elderly to essential hypertension

Nocturnal polyuria is common in the elderly. In this condition the normal c ircadian rhythm of urine production is reversed so that urine flow is highe r at night than during the day. Elderly men with nocturnal polyuria are com monly referred for prostate surgery, which, not surprisingly, fails to reli eve their symptoms. Compared with controls, patients with nocturnal polyuri a have higher nocturnal sodium excretion but not higher nocturnal free-wate r clearance. Similar results have been obtained in children with nocturnal enuresis. Use of vasopressin analogues to induce water retention in elderly patients with nocturnal polyuria is illogical and potentially hazardous; n octuria can be more safely alleviated by diuretic therapy. Nocturnal polyur ia in the elderly is associated with hypertension: this is consistent with studies in younger age groups that show that essential hypertension is asso ciated with nocturia and with increased night/day ratios for sodium excreti on. We propose that nocturnal polyuria and essential hypertension share som e of the same pathophysiological determinants. Specifically, we suggest tha t a defect in the nitric-oxide pathway may lead to resetting of the pressur e-natriuresis relation in the kidney, sodium retention, and compensatory no cturnal natriuresis. This suggestion is consistent with evidence that agein g and essential hypertension are both associated with defects in the nitric -oxide pathway. Our hypothesis has obvious therapeutic implications. More g enerally, studying the pathogenesis of nocturnal polyuria in the elderly ma y advance our understanding of the pathogenesis of essential hypertension.