Nocturia May Mean You Have Sleep Apnea
Nocturia May Mean You Have Sleep Apnea
by
Regina Patrick, RPSGT, RST
If you awaken one or more times during the night to urinate, you may have a commonly overlooked symptom of obstructive sleep apnea: nocturia. A person who has nocturia (pronounced “nok-TOO-ree-uh”) awakens from sleep one or more times to urinate. Nocturia can be caused by lower urinary tract disorders (e.g., enlarged prostate, overactive bladder, bladder inflammation); systemic disorders (i.e., disorders that affect the whole body such as congestive heart failure, diabetes, and metabolic disorders); kidney disorders (e.g., chronic renal failure); drugs (e.g., furosemide [brand name Lasix]); or certain foods (e.g., caffeine, alcohol) that stimulate the production of urine. However, an overlooked problem that may contribute to nocturia is obstructive sleep apnea (OSA). An estimated 40%–50% of people with OSA experience nocturia (using the criterion of ≥2 voids per night).1
In OSA, a person stops breathing intermittently during sleep. The cessation in breathing (i.e., apnea) occurs because the upper airway muscles relax excessively during sleep, which allows soft tissues such as the tonsils and adenoids to be drawn into the airway and block airflow. As the blood oxygen level falls, a person makes increasingly strong efforts to breathe. When the oxygen level has fallen to a certain point, certain cells in the brain trigger the person to arouse briefly (usually lasting a few seconds) to take some deep breaths to restore the oxygen level. During the arousal, snoring and gasping typically occurs. Once the blood oxygen level is restored, the person resumes sleep, which may set the stage for another apnea event.
The most common treatment for OSA is continuous positive airway pressure (CPAP). In this treatment, lightly pressurized air is blown through the upper airway through a mask that fits over the nose or over the nose and mouth. The pressure of the air pushes against upper airway tissues and prevents them from falling into and blocking the airway during sleep.
How OSA contributes to nocturia is unclear. One possibility is through the forces exerted on the organs of the abdomen and chest during an OSA episode. As a person makes increasing efforts to breathe during an OSA episode, the lungs exert increased pressure on the heart. The greater-than normal pressure on the heart causes it to release into the bloodstream a chemical called atrial natriuretic (pronounced "NAY-tree-yoo-REH-tik") peptide (ANP). Once in the bloodstream, ANP is carried to the kidneys, which in response to ANP, increase urine production. The increased amount of urine may then contribute to nocturia.2
Another possibility for how OSA contributes to nocturia may be related to repeated episodes of low blood oxygen that occur with OSA events. Some animal research3 indicates that repeated decreases in the blood oxygen level that occur with OSA may alter how bladder muscles function. For example, muscles may contract more frequently, which may cause a person to have sense of urgency (i.e., a sense having a full bladder that needs immediate emptying) or have to urinate more often. To what extent OSA causes similar changes in bladder function in humans has not been investigated in depth.
Continuous positive airway pressure treatment appears to improve nocturia in some people with OSA.4-6 A possible reason for this improvement is that CPAP treatment may help to restore the interplay among three hormones that maintain proper fluid balance in the body.7 The three hormones are renin (pronounced “REE-nin”), angiotensin (pronounced “AN-gee-oh-TEN-sin”), and aldosterone (pronounced “al-DOS-tuh-RONE”). Insufficient sleep resulting from frequent OSA-related arousals during a sleep period appears to disrupt how these three hormones function together, and consequently increase nocturnal urine production.8 Exactly how insufficient sleep disrupts the normal function of these hormones remains unclear.
Renin helps to increase blood pressure by promoting the production of angiotensin. Angiotensin causes blood vessels to constrict (i.e., shrink), which then increases blood pressure. When blood vessels are constricted, blood has to work harder to pass through them (which increases blood pressure); when blood vessels are more open (i.e., dilated), blood can more easily flow through them (which reduces pressure). Aldosterone helps the body maintain proper blood levels of potassium and sodium, both of which are involved in fluid balance in the body.. For example, when sodium levels are too low, aldosterone causes the kidneys to retain sodium, thereby increasing the amount of sodium in the blood and increasing blood pressure, while releasing potassium into the urine.
In studies7 in which the levels of renin, angiotensin, and aldosterone were measured in patients with CPAP-treated OSA and in patients with untreated OSA, scientists found that CPAP-treated patients had less urine excretion and higher blood levels of renin and aldosterone than did the untreated patients, In addition, the CPAP-treated patients had similar renin activity as that of people without OSA. In addition, CPAP treatment appears to restore the normal daily rise and fall in renin and aldosterone levels so that the greatest amount of urine is produced during the day and least amount is produced during the night.7,8
Some people with OSA may be unwilling or unable to tolerate CPAP treatment. However, nocturia can improve if OSA is treated by other means such as surgery (e.g., UPPP [short for uvulopalatopharyngoplasty; pronounced "YOO-vuh-loh PAL-uh-toh fuh-RIN-go-plas-tee"]), a surgery in which the uvula, tonsils, and other upper airway soft tissues are removed to prevent their collapse into the upper airway during sleep).4
Physicians often do not ask patients complaining of nocturia about symptoms of OSA such as loud snoring, friends and relatives report witnessing the person stopping breathing off and on during sleep, awakening gasping for air, excessive daytime sleepiness. This oversight may place a patient at risk for developing OSA-related problems such as cardiovascular disease (e.g., stroke, hypertension).
If you awaken one or more times to urinate and kidney problems or (in men) prostate problems have been ruled out, you and your physician may need to consider that OSA could be contributing to this symptom—especially if you have symptoms of OSA. A sleep study may be needed to determine whether you have OSA. If so, treating OSA may improve nocturia.
REFERENCES
1. Maeda T, Fukunaga K, Nagata H, et al. Obstructive sleep apnea syndrome should be considered as a cause of nocturia in younger patients without other voiding symptoms. Canadian Urological Association Journal. 2016;10(7-8):E241-E245.
2. Kemmer H, Mathes AM, Dilk O, et al. Obstructive sleep apnea syndrome is associated with overactive bladder and urgency incontinence in men. Sleep. 2009;32:271-275.
3. Witthaus MW, Nipa F, Yang JH, et al. Bladder oxidative stress in sleep apnea contributes to detrusor instability and nocturia. Journal of Urology. 2015;193:1692-1699.
4. Park HK, Paick SH, Kim HG, et al. Nocturia improvement with surgical correction of sleep apnea. International Neurourology Journal. 2016;20:329-334.
5. Rahnama'i M, Degaillier S, Ewoldt T, et al. Reduction of nocturia in patients treated with C-PAP for obstructive sleep apnea syndrome. Bristol, United Kingdom: International Continence Society; 2016. Abstract #9.
6. Miyazato M, Tohyama K, Touyama M, et al. Effect of continuous positive airway pressure on nocturnal urine production in patients with obstructive sleep apnea syndrome. Neurourology Urodynamics. 2017;36:376-379.
7. Follenius M, Krieger J, Krauth MO, et al. Obstructive sleep apnea treatment: peripheral and central effects on plasma renin activity and aldosterone. Sleep. 1991;14:211-217.
8. Kamperis K, Hagstroem, S. Radvanska, E. et al. Excess diuresis and natriuresis during acute sleep deprivation in healthy adults. American Journal of Physiology Renal Physiology. 2010;299:F404-411.
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