Nocturia. A rarely recognized symptom of sleep apnea and other occult sleep disorders

Nocturia, awakening from sleep to urinate, is a common symptom in a variety of medical disorders and in the elderly. Awakening from sleep as a result of nocturia is thought to be secondary to a sensation of urinary urgency resulting from an overextended bladder. Nocturia-related awakenings cause significant sleep disruption and fatigue in elderly patients and are correlated with an increased number of falls at night. Sleep disorders such as sleep apnea are also common in the elderly and are frequently the source of awakenings from sleep. The high incidence of both nocturia and sleep disorders in the elderly and other groups of patients suggests that sleep disorders may be the source of some awakenings from sleep usually attributed by patients to nocturia. Nocturia secondary to sleep disorders would be causatively different from nocturia secondary to pressure to urinate in common medical disorders and would require different diagnostic procedures and treatment.

To determine the frequency of nocturia as a symptom of primary sleep disorders.

Eighty consecutive patients, 27 women and 53 men with a mean (+/-SD) age of 58.7+/-14.1 years, undergoing polysomnography (sleep study or PSG) for the evaluation of a suspected sleep disorder and who met the sole criteria of awakening from sleep at least once and urinating voluntarily. Each patient had either a standard PSG recording or a PSG with administration of nasal continuous positive airway pressure. Immediately after each episode of nocturia during the PSG, patients were questioned about the reason they believed they had awakened. The PSG record immediately before awakening from sleep was then reviewed for potential causes of awakening. Patients were also asked on final morning awakening to fill in a questionnaire regarding their awakenings during the prior night. Patient reports were compared with the PSG to determine the accuracy of subjective reports.

Patients awakened from sleep and voluntarily urinated a mean (+/- of 1.5+/-0.75 times per night for a total of 121 awakenings for the group. The majority (79.3%) of these awakenings from sleep were found to be directly secondary to sleep apnea, snoring or periodic leg movements in sleep. Patients correctly identified the source of their awakening from sleep on only five(4.9%) occasions and only once was sleep apnea correctly cited by a patient as a source of awakening during the night.

Most awakenings from sleep attributed by our patients to pressure to urinate were instead a result of sleep disorders, particularly sleep apnea. The fact that patients do urinate once awake likely contributed to faulty post hoc reasoning and might have limited further inquiry by patients and their physicians in clinical settings into the actual sources of awakening from sleep. Even in those patients with well-known medical reasons for noctruria, Sleep disorders were still found to be the source of almost all awakenings from sleep. Patients were extremely poor judges of the reasons they awoke from sleep. The diagnosis of a sleep disorder should be seriously considered whenever a patient reports frequent awakenings from sleep to urinate.