Nocturia in the Elderly

Article contributed by:

Dr Lawrence Tan, Senior Consultant, Geriatrics Medicine
Khoo Teck Puat Hospital, Singapore
for New Dimension - biannual newsletter of the Society for Continence, Singapore

 

Nocturia is defined by the International Continence Society as the condition of waking up to void one or more times during the night.  The voiding should be preceded and followed by sleep.  Although by definition even a single episode of waking to void is considered nocturia, it is suggested that nocturia is more likely to be significant and bothersome if a patient voids two or more times nightly.

 
Nocturia is a common symptom in the elderly with a higher prevalence with increasing age.  It is one of the most important causes of sleep disturbance and is associated with depression, cognitive dysfunction, accidental falls, poor quality of life and increased mortality.
 

 

On this page: ► Pathophysiology     - Low volume bladder voids     - Increased urine output     - Sleep disturbance     ► Evaluation     - History, Physical examination     - Bladder diary     - Laboratory tests, Other tests	► Management     - Non-pharmacologic     - Pharmacologic

 

Pathophysiology

Nocturia can be attributed to any disorder or condition that causes the following:
 

1. Increased urine output

2. Low volume bladder voids

3. Sleep disturbance
 

1. Low volume bladder voids

This can be due to reduced bladder capacity (overactive bladder) or bladder outlet obstruction (eg. benign prostatic hypertrophy (BPH)).

 
Causes of an overactive bladder include stroke disease, Parkinson’s disease, spinal cord injury, bladder outlet obstruction, bladder stones/tumours and urinary tract infections.
 
2. Increased urine output

An increase in urine output may be due to an increase in urine production over 24 hours (global polyuria) or overproduction of urine only at night (nocturnal polyuria).
 
Global polyuria

Defined as a 24 hour urine volume exceeding 40 ml/kg per day.  For the average 70kg man this works out to 2800 ml per day.
 
Causes: diabetes mellitus and diabetes insipidus.
 
Nocturnal polyuria

In nocturnal polyuria, nighttime urine production is abnormally high relative to the rest of the day.  The definition is age-dependent – for the elderly it has been defined as a nocturnal urine volume greater than 33% of the total 24 hour urine volume.  The measurement should include all the urine produced after going to bed and the first void after rising.
 
Causes:
 

a)	Circadian defect in secretion or action of arginine vasopressin (AVP)   AVP, also known as anti-diuretic hormone (ADH), is the main hormone responsible for regulation of urine production.  It is a peptide hormone secreted by the neurohypophyseal system and is released when plasma osmolality is increased or blood pressure is decreased. There is a diurnal variation in the secretion of AVP in young adults with peak blood concentration during sleeping hours.  In the elderly, however, there is blunting of the nocturnal phase of AVP secretion so that daytime and nighttime blood levels are similar.  This results in as much urine produced in the night as in the day.
b)	Congestive heart failure and conditions causing peripheral oedema (eg. venous stasis, nephrotic syndrome, hepatic failure, hypoalbuminaemia)   In these conditions, extravascular (third spaced) fluids that have accumulated in the lower limbs are reabsorbed into the vascular space leading to a solute diuresis.
c)	Renal insufficiency   Normal ageing is associated with impaired ability of the kidney to retain sodium.  Renal salt wasting in the elderly can lead to a natriuresis and osmotic diuresis
d)	Autonomic dysfunction   A decrease in sympathetic activity can increase urinary sodium excretion resulting in a solute diuresis. Nocturnal polyuria is a common symptom of Parkinson’s disease.
e)	Excessive fluid intake at night
f)	Drugs (eg. lithium, diuretics), alcohol and caffeine

 
3. Sleep disturbance

Respiratory diseases associated with increased airway resistance such as obstructive sleep apnoea can cause nocturnal polyuria through secretion of atrial natriuretic peptide.
 
Obstructive sleep apnoea results in hypoxia-induced pulmonary vasoconstriction which leads to increased right atrial pressure with consequent elevated atrial natriuretic peptide release.
 

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Evaluation

History

Fluid intake:

Ask about fluid intake especially after dinner or at bedtime.  The type of fluids should also be noted as alcohol and beverages containing caffeine can cause polyuria or detrusor overactivity.
 
Medications:

All prescription and over-the-counter medications should be reviewed.  Drugs like tetracycline, lithium and diuretics can cause polyuria.

 
Lower urinary tract symptoms:

Voiding symptoms (hesitancy, weak stream, terminal dribbling) and storage symptoms (urinary frequency, urgency) should be elicited.
 
Medical history:

Diabetes mellitus, congestive heart failure and sleep disorders are relevant in history-taking as these are associated with polyuria.
 
Physical examination

A comprehensive examination should be performed, focusing on the following:
 

a)	Postural blood pressure measurement
b)	Palpation of the abdomen to look for bladder distention
c)	Rectal examination to check for faecal impaction and prostate size
d)	Checking for signs of congestive heart failure
e)	Neurological examination including testing for deficits related to sacral nerve roots eg. perianal sensation, anal tone.
f)	Presence of lower limb oedema

 
Bladder diary

A voiding diary recording the volume and time of each void over 24 hours can be very helpful in determining whether the nocturia is due to low volume voids or increased urine output.

Of note, the first morning void is not counted as a nocturia episode but the measurement of urine volume should include all the urine produced after going to bed and the first void after rising.
 
Laboratory tests

Urea, electrolytes, creatinine, glucose and calcium should be measured.  A urinalysis should also be performed for all patients, with urine culture if urinary tract infection is suspected.  Urine cytology and cystoscopy should be considered if haematuria is present.
 
Other tests

Post-void residual urine measurement with a bladder scanner is useful in patients who might have bladder outlet obstruction or urinary retention.  Urinary flow studies and urodynamic testing may be indicated for further evaluation of suspected bladder outlet obstruction or detrusor dysfunction.  Polysomnography can be performed if symptoms suggest obstructive sleep apnoea.
 

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Management

Non-pharmacologic

a)	Fluid restriction before bedtime
b)	Reduction of alcohol and caffeine intake
c)	Compression stockings or afternoon elevation of legs for peripheral oedema
d)	Pelvic floor exercises and urge inhibition strategies
e)	Continuous positive airway pressure (CPAP) for obstructive sleep apnoea
f)	Neuromodulation – posterior tibial nerve stimulation

 
Pharmacologic

a)	Alpha-blockers and 5α-reductase inhibitors (in men with nocturia related to BPH)
b)	Anti-cholinergic agents (in patients with low volume voids)
c)	Loop diuretics – taken in the afternoon
d)	Melatonin
e)	Desmopressin

 
Desmopressin, a synthetic analogue of AVP can be used in young patients (≤ 65 years of age) who have nocturia despite non-pharmacologic and other pharmacologic therapy.  It has potentially severe side effects notably hyponatraemia and therefore should not be prescribed for older adults over the age of 65.  Serum sodium levels should be normal at baseline and monitored within three days of initiation of therapy.

 

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Article contributed by:
Dr Lawrence Tan, Senior Consultant, Geriatrics Medicine
Khoo Teck Puat Hospital, Singapore
for New Dimension - biannual newsletter of the Society for Continence, Singapore

Dated: December 2015

 

 

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