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Drowsiness behind wheel is common, has many causes (12-27-99)

A gasoline tanker overturns on an interstate highway. A driver runs into college students, killing several of them. Recent incidents remind us that, especially during the holidays, itís better to pull off the road or not even start driving if one is drowsy.

"Sleepiness while driving is a common problem," said Gustavo Román, M.D., professor of medicine at The University of Texas Health Science Center at San Antonio and director of the Sleep Disorders Clinics in the University Health System. "Chronic sleepiness may be caused by a host of undiagnosed disorders, such as sleep apnea. At our center we can observe the snoring and breathing interruptions of sleep apnea and other conditions."

About 100,000 motor vehicle crashes reported to police each year involve drowsy drivers, according to a report in The Journal of the American Medical Association (JAMA). An estimated 4 percent of these crashes cause fatalities. The American Medical Associationís (AMAís) Council on Scientific Affairs "believes the role that sleepiness plays in those crashes is largely underestimated, and drowsy drivers pose a major public health and safety threat," the JAMA article states.

"Drivers may not be getting the quality of sleep they need," Dr. Román said. "Itís very important to go into deep sleep because it is more refreshing. In our modern world, which bombards us with constant stimulation, we have difficulty going to sleep or it is very fragmented."

Sleep involves several stages, starting with drowsiness and progressing to "delta sleep" and "REM sleep." REM, or "rapid eye movement," is the stage of sleep most often associated with dreaming, although dreaming, or some sort of mental activity, can take place during any stage of sleep. An estimated 40 million people in this country suffer from sleep disorders, most of which have not been diagnosed.

Sleep apnea robs sufferers of quality shut-eye. As a person sleeps, the tongue falls backward and blocks the trachea, causing choking and diminished oxygenation. The brain responds with an adrenaline kick to induce shallower sleep and restore the oxygen level. "As he chokes, the person wakes up or reverts to a more superficial stage of sleep; this may occur 250 or more times in one night," Dr. Román said. "The night of sleep ends up being short catnaps, and the person feels sleepy when he wakes up in the morning. The next day he may fall asleep at work, at the dinner table, or worse, on the highway."

The fact that many drivers arenít going to bed at a decent hour is another consideration. "We are a sleep-deprived society," said Paul Ingmundson, Ph.D., board-certified sleep medicine specialist at the Audie L. Murphy Division, South Texas Veterans Health Care System, and clinical professor of psychiatry and neurology at the Health Science Center. "People are sleeping one hour less per day than they did 70 years ago. Socially and culturally we have moved toward a 24-hour day, and sleep has been a casualty."

Weariness can seriously impair judgment. In studying cases of "friendly fire" during the Persian Gulf War, the military identified sleep deprivation as a contributing factor in many of the deaths, Dr. Ingmundson said, adding that the Chernobyl and Three-Mile Island nuclear accidents both occurred in the wee hours of the morning.

The brain operates on its own regulatory clock, known as the circadian rhythm. It causes people and many animals to sleep at night and awake with the sunlight. Any disturbance of this rhythm results in drowsiness.

Scientists have found that, during delta and REM sleep, the brain secretes a chemical called a "delta peptide" which initiates and maintains the deeper sleep stages. "If you canít sleep, or are tired in the morning, you may be building up high levels of this peptide in your spinal fluid," Dr. Román said. "This may be one of the variables affecting sleepy drivers."

The Sleep Disorders Clinic staff collaborates with experts in a variety of fields. Diagnoses lead to treatments for insomnia, narcolepsy, nightmares, sleepwalking, sleep apnea and other sleep disorders. The electroencephalogram (EEG) is one of the instruments used in diagnosis.

Therapies range from masks for sleep apnea patients to surgical procedures. Common sense is not overlooked, either. "We advise patients with sleep disturbances to set an alarm clock for bedtime as well as for waking," Dr. Román noted. The AMA advises drivers not to hit the road during the bodyís natural "down time" (midnight to 6 a.m.).

Anyone interested in the subject or in eligibility for testing may call the Sleep Disorders Clinic at (210) 358-1366. Dr. Román conducts the clinic at University Hospital and the University Health Center Downtown, both components of the University Health System.

Dr. Román would like to see a statewide campaign to encourage sleep management and safe driving. "We could call it, ĎDonít Sleep and Drive,í" he said. A public safety campaign recently publicized by the National Sleep Foundation used the slogan, "Drive Alert, Arrive Alive."

Contact: Will Sansom