Background: Nocturia, a common symptom in the elderly, is often caused by increased urine production at night.
Methods: The present study comprised 17 men and six women aged 68.1 +/- 4.7 (mean +/- SD) years with nocturia (> or = 2 nocturnal voids) and nocturnal polyuria (nocturnal urinary output of > or = 0.9 mL min(-1)). A physical examination, measurements of recumbent blood pressure after a 15-minute rest, plasma AVP assay at noon and midnight, and urine collection performed during a 24-hour period.
Results: The daytime urine output was 1358 +/- 664 mL, and the nocturnal urine output 796 +/- 312 mL. The AVP level was lower at midnight than at noon in 17 persons, and higher at midnight in six persons. Blood pressure was 142.0 +/- 15.7/87.4 +/- 9.1 mmHg. Systolic (but not diastolic) blood pressure increased with decreasing nocturnal plasma AVP. Increasing nocturnal diuresis rate (r2= 0.26; p < 0.01) but not plasma AVP was associated with increasing systolic blood pressure.
Conclusion: In elderly persons with nocturia and nocturnal polyuria, the plasma AVP is low and does not rise nocturnally. The systolic blood pressure is increased with increasing diuresis but unaffected by plasma AVP.