In a previous blog I discussed the relatively new field of forensic sleep medicine. This has become a more recognized and important area of study and practice as sleep related crimes have come to greater attention. Dr. J. Steven Poceta recently published an interesting series of clinical and legal cases in the Journal of Clinical Sleep Medicine. These cases focused on a number of incidents of sleep driving and involved 8 clinical cases (4 men and 4 women) and 6 legal cases (4 men and 2 women).

Sleep driving and drowsy driving are related but different issues. Drowsy driving occurs when people experience sleepiness while driving. This can take the form of brief "micro-sleeps" in which there are short periods of 3 to 10 seconds of being relatively non-responsive to the environment. Obviously this can be quite dangerous as a great deal of roadway can be covered or any number of obstacles can appear in this time. Drowsy driving is generally found to be on par with intoxicated driving in terms of its dangerousness with studies showing impairment comparable to a .08 blood alcohol level (the national legal limit). Drowsiness means the person would fall asleep if given a chance and the head nods and the eyes involuntarily close. A person can be so sleepy that he or she falls completely asleep while driving or while in a low stimulation situation such as sitting at a stoplight. Other drivers tend to help by honking their horns, which usually wakes the person up but which can also startle the sleeper into a sudden, accident-causing movement. These situations can occur in people who have a sleep disorder such as obstructive sleep apnea or narcolepsy. They also often occur after significant sleep deprivation. For example, an individual may lapse into micro-sleep while driving home from class after studying all night for a test, or while driving home from an overnight work shift. I have had patients who, while driving home at the end of a long trip, have had multiple accidents that resulted in thousands of dollars of damage to their cars from, e.g., driving into guardrails.

Sleep driving is different from drowsy driving. It is a variant of sleep walking and occurs when a person enters a sleep state dissociation such that parts of the brain that take care of higher functions are asleep, but motor areas wake up. Amazingly, on occasion patients have driven safely from home to a store and back home again without having an accident. Driving in this condition is absolutely not safe and accidents are highly likely. As with any form of sleep walking, safety measures to guard against sleep driving are needed to prevent people with this problem from getting into their cars while asleep.

Interestingly, with regard to the clinical case series reported by Dr. Poceta, the clinical and forensic cases reviewed all occurred following use of sleeping medication. Patients who presented for evaluation and treatment had experienced episodes of sleep driving following use of zolpidem. Those involved in the legal cases had been arrested for driving while intoxicated. In my clinical practice, most, if not all, of the patients who've presented with similar situations experienced incidents that occurred following use of this sleeping medication. Whether this is due to the specific pharmacology of this drug, or whether this is because it is the most widely used sleeping medication and thus has a higher base rate, is not currently known.

All of these patients showed unusual behavior including confusion and lack of motor control. As with classic alcoholic blackouts, they reported continued interaction with the environment and several hours of amnesia for the events themselves. At times the episodes occurred during the day because the patients took the medication either by accident (e.g. mistaking the sleeping medication for another one that they usually took during the day) or for other reasons such as trying to cope with a severe headache. Those involved in clinical cases reported by Dr. Poceta experienced problems such as being unresponsive to questions while appearing to be awake, appearing intoxicated, or engaging in behaviors such as sleep eating. Those involved in legal cases performed behaviors such as weaving across the highway, hitting other cars, and being unresponsive to police efforts to awaken the driver by using the police car air horn. Dr. Poceta served as an expert witness in these cases and the outcomes ranged from not guilty to reduced charges to conviction. If alcohol was in any way involved it was more likely that the case was closed with a conviction.

Dissociated sleep/wake behavior occurring after the use of zolpidem is a serious problem that can result in accidents and potentially cause fatalities. A number of factors noted in the case series were likely to increase the potential for the occurrence of this behavior. These factors included previous history of a parasomnia such as sleep walking, taking a larger than prescribed dose, lack of careful attention to medicine labels, taking this medication for purposes other than falling asleep, living alone, and using other sedating drugs such as alcohol. I have also had cases where people were sleep walking following use of zolpidem, then went and opened their medication bottle and took additional sleeping pills. They proceeded to engage in sleep eating, intoxicated like behavior or sleep driving. Clearly, appropriated management of this medication is very important.

If you are prescribed this medication be certain to let the prescribing professional know about any previous parasomnias you have experienced such as sleep walking, describe any prior experience with sleeping medication, be sure to take it only as prescribed and only prior to bed time, keep the bottle well labeled and make sure it would be difficult to get to if you were to sleep walk. Most people who use zolpidem do not experience these problems, but enough do that it is wise to be on the safe side. It's better to be cautious than to end up in court!

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