The Odds Ratio Product (An Objective Sleep Depth Measure): Normal Values, Repeatability, and Change With CPAP in Patients With OSA.

STUDY OBJECTIVES

The Odds Ratio Product (ORP) is an objective measure of sleep depth using the relationships of the powers of different electroencephalogram (EEG) frequencies in a single index. The range of the ORP is 0 (deeply asleep) to 2.5 (fully awake). This investigation seeks to elucidate normal values of non-rapid eye movement ORP (ORP) in healthy individuals, repeatability of the measure, and the change in ORP following continuous positive airway pressure (CPAP) treatment.

METHODS

Healthy individuals underwent a home sleep apnea test (HSAT) with EEG followed 1 week later by EEG alone. Another cohort with OSA underwent baseline HSAT with EEG followed by a second EEG study approximately 4 weeks into treatment with CPAP.

RESULTS

Thirty-eight healthy individuals completed the protocol (mean age of 34.9 ± 7.4 years, Epworth Sleepiness Scale score 3.6 ± 2.4, Insomnia Severity Index score 2.0 ± 1.6 and Functional Outcomes of Sleep Questionnaire - shorter version score 19 ± 1.2). The mean ORP for all nights was 0.52 ± 0.13. The difference between the first night and the second night was 0.024 ± 0.17 (not significant). The intraclass correlation coefficient was 0.525, suggesting only moderate agreement between the first and second nights. The normal value for ORP in healthy individuals is ≤ 0.78 units using two standard deviations as the cutoff. Forty participants completed the OSA protocol (mean age 49 ± 11 years, body mass index 35 ± 6 kg/m², apnea-hypopnea index 33.5 ± 28.4 events/h). The mean pre-CPAP ORP was 0.69 ± 0.24 and the mean post-CPAP ORP was 0.57 ± 0.22 (P = .02).

CONCLUSIONS

The ORP proves to have significant variability from night to night in healthy individuals. ORP objectively improves following CPAP treatment, providing further evidence that it measures sleep depth.

CITATION

Penner CG, Gerardy B, Ryan R, Williams M. The odds ratio product (an objective sleep depth measure): normal values, repeatability, and change with CPAP in patients with OSA. J Clin Sleep Med. 2019;15(8):1155-1163.