Comparison of Sleep Latency Measured by the Oxford Sleep Resistance Test and Simultaneous EEG in Japanese Patients

Abstract

Excessive daytime sleepiness (EDS) is observed in various pathological conditions associated with sleep disorders. However, objective methods for the assessment of EDS rely on complex electroencephalographic (EEG) recording and are impractical for use in general clinical practice. To address this issue, the Oxford Sleep Resistance Test (OSLER) has been developed for use in clinical practice overseas, though few studies have examined the reliability of the OSLER test for measuring sleep latency in Japanese patients. Thus, in the present study, we aimed to determine whether sleep latency measured via the OSLER test (SLOSLER) is consistent with that measured via EEG (SLEEG) in Japanese patients with obstructive sleep apnea (OSA). Seventeen Japanese men with OSA (mean age: 51.5 ± 9.8 years) underwent simultaneous OSLER and EEG testing a total of four times on the day following polysomnography evaluation. SLOSLER and SLEEG were compared, and the reliability of the former was analysed using Bland-Altman plots. Mean SLOSLER and SLEEG for all patients were 26.9 ± 11.6 and 25.7 ± 12.2 minutes, respectively. A significant positive correlation was observed between these measurements (p<0.0001, r=0.963). Moreover, the Epworth Sleepiness Scale (ESS) scores were not significantly correlated with either SLOSLER or SLEEG. Bland-Altman plot analysis revealed that 94% of the plotted SLOSLER or SLEEG measurements converged within a range of mean ± 1.96 SD. Our findings thus demonstrated that SLOSLER is consistent with SLEEG in Japanese patients with OSA.