Sleep Apnea May Cause Nighttime Urination

SUNDAY Nov. 29, 2009 -- People who wake up during the night to urinate shouldn't automatically blame a urological problem. Sleep apnea, a breathing-related sleep disorder, could be the cause.

A new study suggests that nighttime urination, or nocturia, is comparable to loud snoring as a marker for obstructive sleep apnea, a disorder in which soft tissue in the throat blocks the flow of air into the lungs, disrupting sleep.

Previous studies established a link between nocturia and sleep apnea, a potentially serious condition that affects about 25 percent of U.S. men and 10 percent of U.S. women, the researchers said. But they believe this is among the first to show that screening for nocturia could help doctors identify patients with apnea.

The study also suggests that a common treatment for sleep apnea -- positive airway pressure (PAP) therapy -- can reduce symptoms of nocturia, thereby improving sleep and preventing debilitating falls among elderly people who get out of bed at night to use the bathroom.

PAP involves wearing a pressurized air mask while sleeping.

Typically, doctors screen for apnea by assessing patients' weight (the condition is associated with overweight/obesity) and asking if they snore heavily, notice breathing problems at night or feel tired during the day (because of interrupted sleep). But because many patients, especially those who sleep alone, are unaware that they snore, apnea often goes undiagnosed.

"When you ask people about symptoms like snoring and gasping, they tend to say, 'No, I don't have them'," said study author Edward Romero, research coordinator at the Sleep & Human Health Institute in Albuquerque, N.M. "But it's very easy for them to realize that they wake up at night to go to the bathroom."

One of Romero's co-authors, institute director Dr. Barry Krakow, said doctors and patients are quick to blame nocturia on diabetes, prostate enlargement and other medical conditions with which it is associated. "I see patients all the time who think they're waking up to urinate because they have prostate trouble or a small bladder," Krakow said. "About 80 percent of the time we discover that apnea is the cause of their problem."

Besides nocturia and snoring, symptoms of sleep apnea include daytime drowsiness, memory problems and depression. Untreated sleep apnea can lead to high blood pressure, blood clots and heart disease.

For the study, published online recently in Sleep and Breathing, the researchers reviewed data on 1,007 adults treated at two sleep clinics in New Mexico between 2005 and 2007. Of the participants, 797 were diagnosed with sleep apnea, 777 reported snoring and 839 reported nocturia. Neither snoring nor nocturia was proof of apnea, but the two symptoms were similar in their power to predict it: snoring was reported by 82.6 percent of apnea sufferers, and 84.8 percent of apnea sufferers reported nocturia.

The authors propose further research be conducted to confirm the effectiveness of nocturia as an apnea screening tool.

Mary Umlauf, a professor at the University of Alabama Capstone College of Nursing in Tuscaloosa and a noted nocturia researcher, said the study could play an important role in dispelling "old wives' tales" about nocturia.

"Many health-care providers and ordinary people think of nocturia as a urological or gynecological problem," she said. "They don't understand that sleep apnea can cause the body to produce too much urine at night.

"People who wake up to urinate shouldn't assume that it's my prostate, or 'I'm just old'," she said.

More information

You can learn more about obstructive sleep apnea at the National Sleep Foundation.

Posted: November 2009


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