Are OSA patients vulnerable to sleep restriction? Effects on sleepiness and perception during simulated driving

Introduction: Obstructive Sleep Apnoea (OSA) is a common disorder with significant neurobehavioural consequences including excessive daytime sleepiness, deficits in sustained attention, and increased motorvehicle accident risk. Healthy, young adult drivers are prone to fallasleep accidents after sleep restriction, but the vulnerability of older, OSA patients to sleep restriction has not been systematically studied. We hypothesise that OSA patients may be less able to compensate and maintain neurocognitive performance following sleep loss than healthy controls. Methods: As part of a comprehensive study of driving and neurocognitive impairment in OSA, we examined preliminary data from 5 severely affected OSA patients (mean [SD]: age = 42.8 [9.9] y; BMI = 43.1 [9.6]; AHI = 68.4 [20.5]/h), and 4 healthy controls (age = 44.25 [9.0] y; BMI = 23.5 [2.8]; AHI = 11.5 [2.7]/h). All completed 90 min of simulated driving in the mid-afternoon following normal (8 h) and restricted (4 h) sleep. Steering deviation, alpha/theta EEG activity and subjective sleepiness/performance were measured throughout. Results: Repeated Measures ANOVA showed significant group (p = 0.043), condition (p < 0.001) and time (p = 0.005) effects on subjective sleepiness. Significant effects were also found on subjective driving performance for group (p = 0.03) and condition (p = 0.015), with a trend for time (p < 0.056). Driving performance data showed differences in steering deviation approaching significance for group (p = 0.059) and time (p = 0.073). Conclusion: Despite considerable inter-individual differences in steering deviation, differences are apparent between OSA and control groups following both normal and restricted sleep. OSA patients are aware of increased sleepiness and resulting impairment compared to healthy controls