Comparison of simulated driving performance in narcolepsy and sleep apnea patients.

Many patients with obstructive sleep apnea (OSA) or narcolepsy have difficulty driving and increased automobile accidents. Previously we have shown that OSA patients perform poorly on a laboratory-based divided-attention driving test (DADT). Patients with narcolepsy may be as sleepy as OSA patients, so we compared performance on the DADT of OSA patients with that of narcolepsy patients. Twenty-one male OSA patients [age 49.3 +/- 12.7 (SD) years; apnea-hypopnea index (AHI) 73 +/- 29] 21 age- and sex-matched controls, and 16 narcoleptics (12 males, four females; age 39.6 +/- 15.2 years) underwent polysomnography followed by daytime sleep latency testing (MSLT). Following a practice session, all subjects were given the DADT for 20 minute prior to each daytime nap of the MSLT. Narcolepsy patients were younger than OSA or controls and more sleepy than OSA patients. Tracking error was much worse in patients than controls (228 +/- 145 cm for OSA vs. 196 +/- 146 for narcolepsy vs. 71 +/- 31 for controls; p < 0.001), although half of either patient group performed as well as controls. There was only a weak relationship between MSLT and tracking in either patient group. We conclude that impairment in laboratory driving performance skills is seen in both groups of sleepy patients but the degree of impairment is difficult to predict from sleepiness alone.

Simulated driving performance in patients with obstructive sleep apnea.

To assist in determining ability to drive in patients with obstructive sleep apnea (OSA), we developed a divided attention driving test (DADT) based on the work of Moskowitz and Burns (6). We first examined its ability to detect impaired performance by testing normal subjects both sober and impaired by alcohol (mean blood alcohol level, 95 +/- 25 mg/dl). Subsequently, 21 male patients with OSA (age 49.3 +/- 12.7 [SD] yr; apnea hypopnea index [AHI] 73 +/- 29) and 21 age- and sex-matched control subjects underwent polysomnography followed by daytime sleep latency testing (MSLT). Before each day-time nap, subjects were given the DADT for 20 min. Patients who performed much worse than control subjects in all measures, with the largest difference noted in tracking error (OSA, 228 +/- 145 cm versus control 71 +/- 31 cm, p < 1 x 10(-9)). Half of the patients were worse than any control subject, with some showing performance worse than control subjects impaired by alcohol. However, MSLT and AHI explained less than 25% of the variance in tracking error, making individual prediction problematic. We concluded that in laboratory driving performance skills are markedly impaired in over half our group with sleep apnea. Further testing and comparing on-road performance should aid in predicting ability to drive.

Effects of nasal CPAP on simulated driving performance in patients with obstructive sleep apnoea.

BACKGROUND: Many patients with obstructive sleep apnoea (OSA) have difficulty in driving and experience increased automobile accidents. It has previously been shown that patients with OSA perform poorly on a laboratory based divided attention driving test (DADT). METHODS: Seventeen men with OSA of mean (SD) age 49.7 (11.2) years and an initial apnoea/hypopnoea index (AHI) of 73.0 (28.9) were restudied from one to 12 (mean (SD) 9.2 (4.2)) months after initiating treatment with nasal continuous positive airway pressure (CPAP) to examine the effects of treatment on DADT performance. Eighteen age and sex matched controls were also retested 8.4 (3.4) months after their initial tests. Following a practice session, all subjects were given the DADT for 20 minutes before each daytime nap of the standard multiple sleep latency test (MSLT). RESULTS: Untreated patients with OSA, who performed much worse than controls in all measures, improved significantly on all measures of performance, particularly in tracking error which returned to the level of controls in all but one patient. Changes in performance were much greater for patients with OSA than for controls in tracking error (mean difference 106 (95% CI 75 to 135) cm), sleep latency/ MSLT (5.3 (95% CI 2.7 to 8.0) min), number of correct responses (1.2 (95% CI 0.4 to 1.9)), number of missed responses (1.7 (95% CI 0.9 to 2.3)), and number out of bounds (10.0 (95% CI 7.9 to 13.6)), but not for response time (0.1 (95% CI -0.3 to 0.2) s). Improvement in tracking error was highly correlated with improvement in sleepiness (r = 0.65). CONCLUSIONS: Impairment in laboratory driving performance skills in patients with OSA is reversed by successful treatment with nasal CPAP. Changes in daytime sleepiness account for some but not all of the improvement.