Nocturnal polyuria in older people: pathophysiology and clinical implications.

OBJECTIVES: To review the physiological changes of aging which affect the systems involved in urine formation and to consider how these changes interact with changes in bladder function, thereby leading to the onset of nocturnal polyuria with associated urinary frequency, nocturia, and incontinence. Based on this information, data are presented on the effectiveness of pharmacological interventions which reduce the rate of urine formation and, thus, can be of benefit in reducing symptoms, especially during the nighttime.
METHODS: Peer-reviewed journal articles were identified by MEDLINE Search and by review of the literature.
CONCLUSIONS: As a consequence of age-associated diminished renal concentrating capacity, diminished sodium conserving ability, loss of the circadian rhythm of antidiuretic hormone secretion, decreased secretion of renin-angiotensin-aldosterone, and increased secretion of atrial natriuretic hormone, there is an age-related alteration in the circadian rhythm of water excretion leading to increased nighttime urine production in older people. The interaction of nocturnal polyuria with age-related diminution in functional bladder volume and detrusor instability results in the symptoms of urinary frequency, nocturia and, in some persons, incontinence. The additional impact of Alzheimer's disease on these physiological and aging changes, as well as on a diminished perception of bladder fullness, leads to an even greater risk of urinary incontinence in these patients. Treatment of nocturnal polyuria with the antidiuretic hormone analog, DDAVP (desmopressin), can result in decreased nocturnal urine production with improvement in symptoms of frequency, nocturia, and incontinence.