Nighttime Urination and Sleep Apnea

Tracy R. Nasca

Nocturia (nighttime urination) is so prevalent in sleep apnea patients it has become a screening tool as significant as snoring. A research study showed that over 84% of patients with sleep apnea reported frequent nighttime urination while 82% acknowledged snoring.

How many bathroom trips do you make during the night? It’s considered normal for one to be awakened once or twice during the night to urinate, but many patients with untreated sleep apnea report as many as 6 or more nightly trips. Often, people assume this disruption of sleep and having a small bladder causes treks to the bathroom.

“Sleep researchers know that nocturia is a sign of sleep apnea,” says Mary Umlauf, Ph.D., associate professor of nursing at UAB and lead investigator of the research study. “However, because the underlying mechanisms linking sleep apnea and nocturia had not been studied before, people with nocturia were more likely to report the problem to their gynecologist or urologist, not a sleep clinician. Doctors most often attribute nocturia to aging in women or to prostate problems in men.”

The study states that “nocturia can be defined as awakening from sleep to voluntarily urinate. It differs from enuresis or bed-wetting, where the person does not arouse from sleep, but the bladder empties anyway. Until recently, nocturia was thought to be caused by a full bladder, but it is also a symptom of obstructive sleep apnea. What actually causes nocturia is still being investigated. Some researchers believe that one event per night is within normal limits; two or more events per night may be associated with sleep deprivation.”

How does apnea cause nocturia? Umlauf explains that during episodes of sleep apnea, the soft structures in the throat relax and close off the airway, setting into motion a chain of physiological events. “Oxygen decreases, carbon dioxide increases, the blood become more acidic, the heart rate drops and blood vessels in the lung constrict,” says Umlauf. “The body is alerted that something is very wrong. The sleeper must wake enough to reopen the airway. By this time, the heart is racing and experiences a false signal of fluid overload. The heart excretes a hormone-like protein that tells the body to get rid of sodium and water, resulting in nocturia.”

The good news is that many people who have nocturia due to their untreated sleep apnea find that it totally resolves once they become cpap compliant. We are aware that the ravages of sleep apnea can and do cause a higher risk of heart problems and stroke. These present serious incentives for patients to strive for successful use of cpap. Nocturia is yet another motivation to become therapy compliant to achieve apnea free, quality, restorative sleep. There are other medical reasons to experience nocturia, so if you suffer with frequent nighttime urination, please discuss with your medical team.

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