At present, there is no simple, objective way to measure the subjective experience of sleepiness -- and, consequently, no simple, objective way to diagnose sleep disorders or to assess the effectiveness of the methods used to treat these diseases. That may soon change, however.
Under a $1.52 million grant from the National Institutes of Health/National Institute of Nursing Research, UIC researchers are investigating the feasibility of using a measure of pupil size as a means of objectively diagnosing sleep disorders like narcolepsy and sleep apnea.
Narcoleptics face irresistible attacks of sleep in broad daylight, caused by a neurological mistiming in their sleep-wake cycle. Those with sleep apnea doze off because their nighttime rest is fragmented -- obstructions in their upper airway passages keep them from getting the amount of deep sleep they need each night.
In medical jargon, these people suffer from "excessive daytime sleepiness," but to what extent?
The method being tested at UIC, called pupillometry, measures the size of the pupil as it oscillates and gradually decreases in size when a person becomes sleepy. Measurements are taken as subjects sit quietly in a comfortable chair in the dark for 15 minutes with their eyes open, trying to stay awake. The readings are used to calculate the extent of pupil oscillation, an indicator of sleepiness. Participants will include people with no sleep disturbances in order to determine a normal range of sleepiness levels.
Currently, two sleep tests based on the electrical activity of the brain, as recorded by an electroencephalogrph, are more commonly used to measure the extent of excessive sleepiness. These two methods, polysomnography and the Multiple Sleep Latency Test, are more expensive, more technologically demanding and more time-consuming than pupillometry.
"The study will help us determine whether pupillometry can be used as an objective measure of sleepiness," said Sharon Merritt, director of the UIC Center for Narcolepsy Research. "If so, we may be able to better screen people for sleepiness and objectively monitor the effectiveness of treatment for people who have sleep disorders that cause excessive daytime sleepiness."
The UIC Center for Narcolepsy Research brings together a multidisciplinary group of researchers to investigate sleep disorders, including narcolepsy and sleep apnea syndrome. The center also studies the biobehavioral impact of excessive daytime sleepiness on individuals and their families. The center is part of the UIC College of Nursing, one of the top ten nursing schools in the country.
With 25,000 students, the University of Illinois at Chicago is the largest and most diverse university in the Chicago area and is one of only 88 national Research I universities. Located just west of Chicago's Loop, UIC is a vital part of the educational, technological, and cultural fabric of the entire metropolitan region. Visit http://www.uic.edu for more information.