0317 Normal Values and Repeatability of a Novel Sleep Depth Scale; The Odds Ratio Product

Abstract

Introduction: The Odds Ratio Product (ORP) has recently been described as a method of objectively measuring sleep depth using the relationships of the powers of different EEG frequencies in a single understandable index. The scale ranges from 0 - 2.5 with values of zero only occurring during sleep and a value of 2.5 only occurring during wakefulness. A value of 1.25 predicts an equal probability of being awake or asleep. The current investigation is undertaken to obtain normal values of non-REM ORP in good sleepers in their home environments and to establish the repeatability of this measure from night to night. Methods: Good sleepers (GS) were recruited and defined as nonshift workers sleeping 7-9 hours per night who considered their sleep of good quality and didn't have daytime symptoms attributed to their sleep. Acceptable participants couldn't be habitual nappers, have chronic health or sleep diagnoses, use psychotropic or recreational drugs, or have reached the menopause. ESS, ISI and FOSQ 10 had to be in the normal range. OSA was excluded based on an HSAT measuring EEG (Prodigy). A second EEG study was performed one week later. Results: Thirty-three people completed the study (9 (20-35) females, 8 (20-35) males, 8 (35-50) males and 8 (35-50) females. The mean ORP for non-REM sleep during both nights of the study was 0.54 ± 0.17 (66 nights). Excluding three outlier nights, results in a tighter distribution of 0.51 ± 0.13. Distribution fitting suggests a normal distribution (Kolmogorov-Smirnov test, p=0.254). No difference was noted in non-REM ORP between first and second nights (0.55 ± 0.17 vs 0.53 ± 0.16). The study was powered to find a difference of 0.08 units between first and second nights with an α error (0.05) and β error (0.2). Conclusion: GS normal values for non-REM ORP is ≤0.76 units. Repeatability of ORP suggests no systematic second night effect. There is considerable variability in non-REM ORP between nights.