Diagnosing Kids’ Sleep Apnea in a Cup

800px-sleeping_babyWhen an adult snores, it’s annoying. When a kid snores, it’s mostly cute. But as David Gozal, chairman of pediatrics at Comer Children’s Hospital explains, those nighttime noises aren’t always innocuous.

“Snoring is not benign in kids,” Gozal said. “Snoring is clearly something that we need to not just make fun of but actually think that it has consequences on learning, behavior, the cardiovascular system, and diabetes. It can also exacerbate many existing conditions associated with learning, intelligence and behavior.”

“Those effects are silent for the most part in children, but nevertheless, if let go for a long time, they can cause damage that could be irreversible and lead to onset of disease in adults earlier and more severe than otherwise would be appropriate.”

Yet while awareness and diagnosis of sleep disorders in adults has improved over recent years, the pediatric end of the field has lagged somewhat behind. Conducting an overnight sleep study – which involves a night in the hospital or sleep center bed attached to a multitude of wires – is unpleasant enough for adults; just try performing one on a sleep-deprived 8-year-old. The number of sleep technicians and doctors trained to record and analyze the unique characteristics of sleep in children is also a fraction of those available for adult studies, Gozal said. That means very few sleep centers are able to conduct sleep studies in children, which produces waiting lists as long as one year in some areas.

And yet, better screening technology is needed to sort out relatively harmless “primary snoring,” seen in around 1 out of every 10 kids, from the more harmful obstructive sleep apnea (OSA). Often associated with adult, overweight males, OSA reflects the occurrence of frequent breathing “pauses” during sleep, which may lead to as many as hundreds of  short episodes without oxygen and abrupt awakenings during a single night of sleep. Gozal’s research found that about 3 percent of children suffer from OSA, but the condition is often undiagnosed, and sometimes even treated (through surgical removal of the tonsils and adenoids) based upon mere reports of chronic snoring.

“This is not a trivial proposition,” Gozal said. “And yet because there’s so little choice, parents and physicians decide to pursue surgery because there’s not enough access to the diagnostic tool. If it were easy, and not as expensive and inconvenient, it would allow everybody to get tested and know whether you have sleep apnea or you don’t before going to surgery.”

That’s the kind of clinical problem that inspires creative science, and Gozal’s research group at his old home, the University of Louisville, and his new, the University of Chicago, have been working toward a simpler way of testing children for obstructive sleep apnea. Recognizing that OSA causes changes in kidney function in mice and humans, Gozal hypothesized that kids with sleep apnea could be identified due to differences in what comes out of their kidney: urine. By measuring the proteins from kids diagnosed with OSA and comparing their “urinary proteome” to kids without the sleep disorder, Gozal’s team hoped to identify candidate proteins that could be used in, simply put, a pee test for sleep apnea.

In theory, such a screen would work like a home pregnancy test – do your business on a specially-treated strip and wait to see if a plus sign (or more likely, as I’ll explain, three plus signs) appear. Pregnancy tests are actually a home version of a common laboratory technique called ELISA, used to identify whether a particular protein is in a sample. Gozal’s group first had to find what proteins the test would look for, and were fortunate enough to find 12 that were either increased or decreased in the urine of children with OSA. Of those 12, ELISA tests were either developed or adapted for four proteins and were deemed reliable enough to serve as markers of OSA – each one predicted the diagnosis of OSA 75 percent of the time, but combining the four proteins in one assay successfully predicted OSA in 95 percent of the cases analyzed.

That’s a pretty encouraging result, but only the first step towards a true test, Gozal said. Since the current test was reverse-engineered from children already diagnosed with OSA, the next phase involves testing many children who haven’t yet been tested for a sleep disorder, then comparing the results to those of overnight sleep studies. If successful, further time will be needed to modify the test for home use, though Gozal said hospitals are currently equipped to carry out the test in its current form.

And once the test has been proven effective and easy to use in children, the next step could be an adaption to screening adults with sleeping problems – spending the night attached to wires in a hospital bed is no fun for 48-year-olds either. But that transition is easier said than done, Gozal said.

“Kids through their lives are more predictable than adults,” Gozal said. “Adults may drink alcohol, smoke, or already have cardiovascular disease, obesity or diabetes. All that will change the way the kidney behaves, so it makes it more difficult.”

About Rob Mitchum (526 Articles)

Rob Mitchum is communications manager at the Computation Institute, a joint initiative between The University of Chicago and Argonne National Laboratory.

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