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The authors used a divided attention driving test (DADT) previously shown sensitive to impairment by alcohol and to similar impairment in half of sleep apnea patients prior to treatment, to compare 21 untreated sleep apnea patients, 16 untreated narcolepsy patients, and 21 healthy controls subjects. They found both patient groups performed much worse than the controls, making about three times as many errors. As they put it, over half the sleep apnea and narcolepsy (see Glosssary) patients did worse than the worst subjects in the control group; but conversely, there were many patients who performed as well as the controls. However, neither apnea/hypopnea indices (see Glossary) (which averaged high at 73/hr for sleep apnea patients) nor results of Multiple Sleep Latency Testing (see Glossary) (with short sleep latencies averaging 4.9 minutes for narcolepsy patients, intermediate at 7.9 mins for sleep apnea patients, and normal at 13.2 mins for controls) failed to discriminate "good" from "bad" drivers.
The authors acknowledged the limitations of a lab-based simulation test such as the DADT but pointed out that actual driving tests with an observer present have limitations, too, such as the "alerting" effect of being under direct scrutiny while driving. They also refer to studies from various countries documenting excess numbers of accidents in sleep-disordered patients. The authors had previously found the performance of sleep apnea patients on the DADT to improve with CPAP (see Glossary) treatment. |
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Whether one uses a laboratory test like the DADT or direct reports of accidents, it seems clear that untreated sleep disorder patients, including those with sleep apnea, often--but now always--have impaired driving ability. This study, which was designed to focus on patients with narcolepsy, showed that this group and the sleep apnea group had about equal degrees of impairment compared to normal controls. The impairment, at least on this test, was substantial, putting half the patients quite outside the range of normals.
The study found such standard measures of severity of sleep apnea and narcolepsy as the apnea/hypopnea index and the multiple sleep latency test not predictive of which patients would show the most impairment on the simulated driving test. However, it has been shown that appropriate treatment of both disorders improves performance. The results of this study therefore apply mainly to untreated sleep apnea patients. One might suspect they would also apply to inadequately treated apnea patients, but the study did not test this. One conclusion might be that sleep apnea patients who fail to get treatment put themselves at risk of substantial driving impairment, similar in magnitude to drunk drivers, with associated increased risk of auto accidents. Since the apnea/hypopnea index, which showed a wide range (though the minimum was 15) in these apnea patients, failed to predict performance, one could not say that one was a safe to drive untreated just because one had only "mild" sleep apnea. Until and unless some widely accepted test is developed to identify untreated sleep apneics who are "safe" to drive, all must draw suspicion of being impaired drivers. Unlike alcoholic drivers, for whom breath and blood tests for alcohol levels allow one way of determining present impairment, untreated sleep apneics with driving impairment must be presumed chronically impaired--though quite likely the actual degree of impairment would vary with the degree of their sleepiness, not so objectively measurable at a given moment in time in an actual driving situation. Thus, sleep apnea patients who fail to get treatment may put themselves and others at risk of accidents when they drive, and may soon find themselves at risk of losing licenses if, as seems to be the case, the doctors who diagnose them come to share responsibility for accidents if they know the patient is untreated yet continuing to drive. The sleep apnea patient who chooses not to get treated may lose the option to drive as public awareness of this problem grows. Hopefully, this risk will not extend to those who do get treated. However, we must recognize that some apnea patients under treatment remain quite symptomatic for lengthy periods, and for these individuals some objective way of determining whether or not their driving is impaired may be crucial. In my own experience, during 6 years of CPAP treatment I continued to have excessive daytime sleepiness which, thankfully, did not cause any serious accidents. Though I was quite aware of my driving being impaired by sleepiness, I thought it would be impossible to give up. Finally a very minor accident occurred when I fell asleep at the wheel while standing still in traffic, letting go of the brake. When my sleep doctor heard of this, he insisted I stop driving until my BiPAP (see Glossary) treatment had been adjusted to an effective level. Prohibition from driving would be a major disruptive event to many people. In my case, I had already stopped working because of my symptoms, so the impact was less: I didn't need to commute, I could depend on my wife and stepson to drive me long distances to appointments, and I lived within walking or bicycling distance of a lot of stores and other resources. Many people would not be so fortunate. |
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