Section 7:
Diseases of the Nervous System

7.3 Sleep Disorders

Sleep Apnea and Other Measures of Performance

Researchers have attempted to identify performance deficits associated with sleep apnea that may have relevance for driving. In that regard, studies have been done comparing the performance of individuals with sleep apnea to that of controls on driving simulators, computer programs simulating aspects of driving (Steer Clear), divided attention driving tasks (DADT), and the PVT (Psychometer Vigilance Test device). The results of those studies are summarized in Table 19.

In the first study listed in Table 19, Findley et al. (1989) compared the performance of patients with sleep apnea to that of age- and sex-matched controls. Performance was assessed by means of a computer program (Steer Clear). This program graphically displays a moving automobile, a two-lane highway, and intermittent obstacles in the highway. Subjects are to avoid hitting obstacles by changing lanes with a single computer key. The outcome measure is the number of obstacles hit during the 30-minute 'simulated drive'. Performance also was assessed by means of a Doran driving simulator, with number of steering, signaling, braking, accelerating, and speeding errors measured. The outcome measure was a percentage correct score. As can be seen in Table 19, subjects with sleep apnea performed significantly poorer in terms of obstacles hit (Steer Clear) and in terms of percentage correct (Doran Simulator score) compared to controls. In a later study, Findley et al. (1991) examined the relationship between performance on Steer Clear and crash rates. Results of that investigation revealed that individuals with very poor performance on Steer Clear had higher crashes/driver/5 years (0.38) than individuals with poor performance (crashes/driver/5 years = 0.20) or those with normal performance (crashes//driver/5years = 0.05). However, as noted earlier, individuals with sleep apnea and narcolepsy were included in the sample. It is unclear from the data the percentage of sleep apnea patients and narcoleptic patients included in each of the above categories. Also unclear is the criterion used for performance classification. It is interesting to note that results from this investigation revealed that 31 percent of the patients with sleep disturbances (narcolepsy or sleep apnea) performed within normal limits on Steer Clear.

Table 19  Summary of Studies Examining Differences in Performance on Simulators and Other Performance Measures Between Individuals with Sleep Apnea (SA) and Controls (C)