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The authors note that sleep-disordered breathing, as a cause of excessive daytime sleepiness, is of special concern because of its high prevalence and the fact that most sufferers are as yet undiagnosed and untreated. Studies have shown that patients with OSA perform poorly on driving simulation tests and have an accident rate 2-7 times as high as people without OSA. The accident rate of OSA patients decreases significantly after 1 year of treatment with CPAP. The study sample consisted of 913 licensed drivers, ages 30-60, who had undergone an overnight sleep study protocol and interview regarding driving habits and situational sleepiness. State records of 5-year motor vehicle accident history were obtained for all subjects, with polysomnography completed at various points during this 5-year interval for different subjects. For classification, AHI cutoffs of 5 and 15 were used; those with AHI less than 5 and no history of snoring were considered free of sleep disordered breathing. The potential confounding and interactive effects of age, miles driven, and alcohol consumption were taken into account statistically. The subjects included 542 men (59%) and 371 women (41%), averaging 45 years of age (SD=8), 318 (35%) of whom had no evidence of sleep-disordered breathing, 374 (40%) of whom had only a history of snoring (with an AHI less than 5), 133 (15%) had AHIs in the range of 5-15, and 88 (10%) had AHIs over 15. Over the 5-year study period, the 913 participants were involved in a total of 227 motor vehicle accidents. Of those with at least one accident, 13% had more than one. There were no immediate fatalities from these accidents. Men with sleep-disordered breathing, compared to those without SDB, had three times the risk of having had an accidents; but this risk did not increase with SDB severity. There was no such relationship for women. But the risk of multiple accidents was increased for both men and women, about five times the risk of people without SDB. Including measures of sleepiness (such as the Epworth Sleepiness Scale and the Multiple Sleep Latency Test) did not add anything to the results. The authors considered their data to provide the first evidence of a link between polysomnographically determined sleep-disordered breathing in the general population and objectively measured history of motor vehicle accidents. In the most severe instance, men and women with AHIs greater than 15 were seven times as likely to have had multiple accidents during the five year period as those without SDB. The fact that their data did not support an independent role of sleepiness as a factor in risk of motor vehicle accidents was interpreted as a lack of adequate sensitivity and specificity of their measures to sleepiness relevant to driving performance. The authors acknowledged that the relatively low number of accidents (only 165 participants had one accident and only 24 had multiple accidents) means a wide range of uncertainty for the exact quantitative risk, so that the true values might range between something of little practical significance and something that could explain a large proportion of all accidents. This also made it difficult to reliable relate accident risk to severity of sleep disordered breathing. They also acknowledged that both trivial accidents (for which no state report is mandated) and more serious single-car accidents which the driver didn't report for fear of insurance repercussions, would be absent from their records. They speculated about the apparent difference between women and men in relation of SDB to risk of accidents as possibly relating to the greater ability of women to perceive their own sleepiness and take countermeasures, or the tendency of men to go on driving despite sleepiness, related to greater male tendency to risk-taking behavior. The limitation of their sample to employed persons might result in underestimation of risk if driving impairment due to SDB has kept people out of work but not off the road. Another factor which might yield underestimation of risk is the fact that for some subjects, polysomnography took place in the first year of the five-year accident history, so that subjects could take precautions or get treatment in the meantime. They noted that, lacking compelling evidence that apnea in itself increases driving risk, a committee of the American Thoracic Society recently concluded that pulmonary specialists should warn apnea patients against driving while sleepy but decisions on driving restrictions could be made on a case-by-case basis, using measurement of sleepiness as one factor to assess risk. The authors disagree with the adequacy of this approach because perceived sleepiness by itself did not contribute to risk and cannot therefore be used as a warning sign to avoid unsafe driving. Rather, they suggested that all patients with sleep apnea be warned against driving while untreated. Motor vehicle accidents, unlike the other consequences of sleep apnea (like hypertension), put the general public at risk and may justify placing driving restrictions on individuals with untreated sleep apnea. Furthermore, the morbidity, mortality, and property damage associated with motor vehicle accidents must be added to the economic and human costs of letting sleep apnea go undiagnosed and untreated.

This is the third article reviewed here on this topic--the others being #1 and #6. This reflects the importance I give to it. Set aside for a moment the mounting evidence, and give some thought to what you believe to be the truth of the matter. I believe that sleep apnea does contribute to dangerous driving and accidents. I have often driven dangerously while sleepy or half-asleep. Moreover, I have used poor judgment at such times. Rarely have I pulled over to rest. Usually I tried to make it to wherever I was going, often because I felt I had to be on time for something, sometimes because I felt I could rest more comfortably at home. I ended up having only one very minor accident, but I could easily have caused many more, letting my car drift out of its lane. For me, the half-asleep state resembles drunkenness in that judgment is impaired, and concern for consequences is blunted or absent. Many times my wife has asked if I was alert, and usually I said yes, even when I wasn't. Sometimes she would complain about my driving erratically and I would deny it, even making fun of her well-founded worries! Can any of you relate to this sort of thing? Once I tried to do a study of driving impairment due to sleepiness in apnea patients on CPAP at a V.A. Basically, everyone denied it. As a V.A. doctor, I might have seemed to them like a government official, who might take away their licenses even though I claimed any information they gave me was confidential. What seems still unclear is the exact magnitude of the driving risk associated with sleep apnea. It may be as high as driving under the influence of alcohol. The difference is that alcoholics can driver sober and prove it with a breath test, where it isn't so easy for a sleep apneic to prove alertness. The alertness of a sleep apneic, unlike the sobriety of an alcoholic, can be constantly in question, regardless of what the apneic does or doesn't do--even getting treated. Who doubts that many sleep apneics go quite a while in treatment before getting straightened out? Some never do get complete relief of symptoms. To the extent that the threat of accidents forces third parties to pay for diagnostic polysomnography and CPAP, this is good news. To the extent that the threat of losing a license forces a reluctant sleep apneic into getting worked up and treated, this is also probably a benefit. But how will one be sure when the apneic has been treated effectively enough to drive safely? Recall the assignment of responsibility to pulmonologists for warning patients. If doctors start to feel they share the responsibility for accidents if they fail to warn, they will warn increasingly, which will put more and more responsibility on patients to not only get treatment, but to refrain from driving or to self-report their possible impairment to the driver's license bureau, with unpredictable consequences. Loss of the ability to drive, while not necessarily a catastrophe, can certainly be disruptive. Even though I had already stopped working when my doctor told me to stop driving, I was still in a difficult position. My wife had to drive me to appointments; I had to schedule things like that around her days off. Eventually I unwisely stopped treatment with doctors who were too far away, as I felt it was burdensome to her. It was also burdensome to her to have to taxi the kids around everywhere; we couldn't share this responsibility any more. There was a lot of pressure on me to drive. I'm still debating what to do with my license, up for renewal soon--whether to report myself as having this problem which may end up with my license being suspended. What would you do?

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