Accuracy of the Oxford Sleep Resistance Test versus Simultaneous Electroencephalography to Detect Sleep Onset

Background: The Oxford Sleep Resistance test (OSLER) is a useful tool to assess daytime vigilance. However, it has not been validated against simultaneous electroencephalography (EEG) recordings in large populations. The main objective of the study was to compare the OSLER values versus EEG-determined Sleep Onset latency (EEGSOL). Methods: Patients referred for assessment of daytime vigilance were recruited from a tertiary sleep clinic. Patients underwent the OSLER (4 x 40 minutes trials; if 7 consecutive stimuli are missed, the trial is terminated and sleep onset is concluded to have occurred) with simultaneous EEG recordings. Determination of EEG-SOL using American Academy of sleep Medicine (AASM) criteria to score sleep during daytime testing was compared to OSLER values. Results: 65 OSLER were performed in 65 subjects for a total of 260 trials (65X4 trials/OSLER). In 136 out of the 260 trials (52.3%), subjects remained awake according to the OSLER, while EEG-SOL was scored in 5 of the 136 trials (3.7%). Of the 124 trials (47.7%) with sleep onset, (i.e. 7 consecutive missed stimuli) the mean sleep onset value was 14.5 ± 10.9 min and EEG-SOL was recorded before the end of the trial in 37 trials (29.8%) (Mean difference EEG-SOL vs. OSLER 4.1 ± 5.8 min). Conclusion: Using current AASM criteria for daytime testing, EEG-determined sleep onset latency is unlikely to occur in subjects with no sleep onset in the OSLER. However, the presence of sleep onset in the OSLER cannot be used as a precise surrogate to detect EEG sleep onset.