Background: Because of previous sleep disturbance and sleep hypoxia, patients with obstructive sleep apnea (OSA) might be more vulnerable to the effects of alcohol and sleep restriction than healthy persons.
Objective: To compare the effects of sleep restriction and alcohol on driving simulator performance in patients with OSA and age-matched control participants.
Design: Driving simulator assessments in 2 groups under 3 different conditions presented in random order.
Setting: Adelaide Institute for Sleep Health, Sleep Laboratory, Adelaide, Australia.
Participants: 38 untreated patients with OSA and 20 control participants.
Measurements: Steering deviation, crashes, and braking reaction time.
Intervention: Unrestricted sleep, sleep restricted to a maximum of 4 hours, and ingestion of an amount of 40% vodka calculated to achieve a blood alcohol level of 0.05 g/dL.
Results: Patients with OSA demonstrated increased steering deviation compared with control participants (mean, 50.5 cm [95% CI, 46.1 to 54.9 cm] in the OSA group and 38.4 cm [CI, 32.4 to 44.4 cm] in the control group; P < 0.01) and significantly greater steering deterioration over time (group by time interaction, P = 0.02). The increase in steering deviation after sleep restriction and alcohol was approximately 40% greater in patients with OSA than in control participants (group by condition interaction, P = 0.04). Patients with OSA crashed more frequently than control participants (1 vs. 24 participants; odds ratio [OR], 25.4; P = 0.03) and crashed more frequently after sleep restriction (OR, 4.0; P < 0.01) and alcohol consumption (OR, 2.3; P = 0.02) than after normal sleep. In patients with OSA, prolonged eye closure (>2 seconds) and microsleeps (> 2 seconds of theta activity on electroencephalography) were significant crash predictors (OR, 19.2 and 7.2, respectively; P < 0.01). Braking reaction time was slower after sleep restriction than after normal sleep (mean, 1.39 [SD, 0.06] seconds vs. 1.22 [SD, 0.04] seconds; P < 0.01) but not after alcohol consumption. No group differences were found.
Limitation: Simulated driving was assessed rather than on-road driving.
Conclusion: Patients with OSA are more vulnerable than healthy persons to the effects of alcohol consumption and sleep restriction on various driving performance variables.
Primary funding source: Australian National Health and Medical Research Council.