Many conditions can result in nocturia but it is mostly associated with increased night-time urinary volume and bladder storage difficulties.

Increased night-time urinary volume

Nocturnal polyuria

Nocturnal polyuria literally means that you wake up at night (nocturnal) one or more times (poly) to urinate/void (“uria”). It is the no.1 cause of nocturia in Hong Kong. Young people who produce more than 20% of their total urine during sleep and older people pass more than 33% of their daily total at night are usually considered to have nocturnal polyuria. Nocturia polyuria mainly results from the age-related changes in the circadian rhythm of urine excretion, however other factors can also contribute to the onset of nocturnal polyuria, such as:

  • Abnormal vasopressin (ADH) secretion
  • Drug toxicity or side effects
  • Re-absorption of third space fluid
  • Dietary intake: excessive drinking (including alcohol) and consumption of diuretics before bed time
  • Sleep apnea
  • Cardiac failure
  • Untreated diabetes mellitus
  • Renal failure

Polyuria is defined as an excessive volume of urination for an adult of at least 2.5 liters of urine per day. People with polyuria usually undergo further investigation to see whether it is due to conditions like:

Reduced bladder storage

Reduced structural bladder capacity

Reduced structural bladder capacity is caused by fibrosis, previous radiation therapy or carcinoma in situ.

Reduced functional bladder capacity

Reduced functional bladder capacity mainly results from an uninhibited overactive bladder.

Other factors

Pharmacological causes:
  • Medications contain xanthines (i.e. theophylline, caffeine) and beta-blockers
Psychological causes:
  • Anxiety disorder
  • Learned voiding dysfunction
Physiological problems:
  • Imbalance of night-time urine production and bladder capacity
  • Detrusor instability
  • Neurological disorders (e.g. multiple sclerosis)
  • Bladder hypersensitivity
  • Bladder outlet obstruction
  • Urogenital ageing
  • Bladder cancer
  • Bladder calculi

You may follow this link to learn about the treatment of nocturia.


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