Latest research on obstructive sleep apnea

Urine test for pediatrics, plus link to ecstasy

Researchers at the University of Chicago have discovered a technique that is able to determine whether a child has obstructive sleep apnea (OSA) by screening their urine.

"These findings open up the possibility of developing a relatively simple urine test that could detect OSA in snoring children. This would alleviate the need for costly and inconvenient sleep studies in children who snore, only about 20% to 30% of whom actually have OSA," said lead author David Gozal, MD, professor and chairman of the Pediatrics Department at the University of Chicago. The study results are published in the Dec. 15 issue of the American Thoracic Society's American Journal of Respiratory and Critical Care Medicine.

Gozal and researchers from University of Chicago and the University of Louisville studied 90 children who were referred to the sleep clinic to be evaluated for suspected sleep disordered breathing. They also recruited 30 healthy, nonsnoring children from the community to serve as controls. The children all underwent standard overnight polysomnography and were categorized as having OSA, habitual snoring or no sleep-disordered breathing.

The children's first sample of urine was collected the morning after the sleep study. The researchers used a sophisticated electrophoresis technique to screen hundreds of proteins simultaneously and found that a number of the proteins were differently expressed in children with OSA compared to children with habitual snoring or healthy, nonsnoring children. "It was rather unexpected that the urine would provide us with the ability to identify OSA," said Gozal. "However, the field of biomarkers is one that is under marked expansion, and this certainly opens the way for possible simple diagnostic screening methods in the future."

While it is estimated that 1%-3% of all children up to the age of 9 may suffer from OSA, many more (up to 12%) experience habitual snoring. Because OSA can lead to cognitive, behavioral, cardiovascular, and metabolic consequences in children, differentiating it from habitual snoring is essential. The initial approach is surgical by removing the enlarged tonsils and adenoids, and some children might end up needing CPAP after their surgery.

"We wish to validate these findings in urine samples from many children from laboratories around the country and to develop a simple color-based test that can be done in the physician office or by the parents," said Gozal.

Ecstasy use may lead to sleep apnea

Repeated use of the drug known as "ecstasy" significantly raises the risk of developing sleep apnea in otherwise healthy young adults with no other known risk factors for the sleep disturbance, a new study by Johns Hopkins scientists suggests.

The finding is the latest highlighting the potential dangers of the amphetamine-style chemical used illegally by millions of people in the United States. The Johns Hopkins scientists note that sleep apnea itself can lead to an assortment of health problems, including a decline in cognitive function, an increased risk of diabetes, and an increased risk of death from heart disease.

"We know that abusing drugs can have numerous harmful effects. Our findings show yet another reason not to use ecstasy," according to lead researcher Una D. McCann, MD. Users claim the drug enhances intimacy, diminishes anxiety, and facilitates some forms of psychotherapy.

The team led by McCann, professor in the Department of Psychiatry at the Johns Hopkins University School of Medicine, previously linked ecstasy, or methylenedioxymethamphetamine (MDMA), to a variety of neurological problems, including subtle cognitive deficits, impulsive behavior, and altered brain wave patterns during sleep. These problems are thought to arise from the drug's targeted toxic effects on neurons that produce the hormone serotonin. Studies in animals and people have shown that MDMA use shortens the filament-like ends of these nerve cells, preventing them from making normal connections with other neurons.

Because these cells regulate multiple aspects of sleep, McCann's team recruited 71 sleep study volunteers, all MDMA users, by advertising for "club drug users" in newspapers and fliers. All had typically used other recreational drugs as well. They also recruited 62 participants who had similar patterns of illegal drug use but had never taken MDMA. The MDMA users had taken the drug at least 25 times in the past, a number previously shown to have lasting effects on serotonin neurons. All of the volunteers were otherwise physically and mentally healthy and had abstained from drug use for at least two weeks prior to the study.

To evaluate the participants' breathing patterns during sleep, each volunteer spent a few nights at a sleep research center. From "lights out" at 11 p.m. to "lights on" at 7 a.m., study volunteers slept while hooked up to a variety of devices to measure breathing, including airflow monitors at their noses and mouths and bands around their chests and abdomens to measure expansion. The researchers diagnosed sleep apnea by counting the rate of incidences of shallow or suppressed breathing, with mild apnea requiring five to 14 of these incidences, moderate apnea requiring 15-29, and severe apnea requiring 30 or more.

Results published in the Dec. 2, 2009, issue of Neurology, the medical journal of the American Academy of Neurology, showed that rates of mild apnea were similar between the two groups, with 15 MDMA users and 13 other volunteers affected. However, while eight MDMA users had the moderate form of apnea and one had the severe form, none of the other volunteers had either of these more serious forms. Results showed that the more participants had used MDMA in the past, the more severe their apnea was likely to be.

Known risk factors for sleep apnea include older age, obesity, and other medical conditions. However, McCann says, of the 24 ecstasy users who had sleep apnea, 22 were age 31 or younger, and none had any known serious medical problems. "Our subjects were otherwise healthy young adults, so this is a very surprising finding," she says.

Though the researchers suspect that the cause for the MDMA users' sleep apnea centers on affected serotonin neurons, the exact mechanism remains a mystery. McCann explains that these neurons appear to help sense blood oxygen levels, control airway opening and generate breathing rhythms. Any of these pathways could be separately influenced by ecstasy use, she says. The researchers are working to tease apart which pathway is at play in MDMA users.