Sultan Qanash1, Eleni Giannouli2, Magdy Younes3. 1. Sleep Disorders Centre, Department of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada; King Saud Bin Abdulaziz University for Health Science, King Abdullah International Medical Research Center, Jeddah, Saudi Arabia. 2. Sleep Disorders Centre, Department of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada. 3. Sleep Disorders Centre, Department of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada; YRT Ltd, Winnipeg, Manitoba, Canada. Electronic address: mkyounes@shaw.ca.
Abstract
OBJECTIVES: Depth of sleep within non-rapid-eye-movement (non-REM) stage-2 (N2-depth) varies from being nearly similar to stage-1 to nearly similar to stage-3. Differences in N2-depth are not captured by conventional indices of sleep depth (N1-N3 times, arousal/awakening index) when comparing sleep depth under different conditions. Magnitude of changes in N2-depth in the same individual under different experimental conditions, and the importance of measuring these changes are unknown. METHODS: We measured sleep depth using the odds-ratio-product (ORP), a continuous index of sleep depth (0 = deep sleep, 2.5 = full wakefulness) (Younes et al. (2015) ORP of sleep EEG as a continuous measure of sleep state. Sleep 38(4):641-54.). ORP in stage 2 (ORPN2) and in all non-REM (ORPNR) were measured, along with conventional indices (1) in the first and second halves of the night in 34 patients with no pathology, and (2) before and on continuous positive airway pressure (CPAP) in 75 patients with obstructive apnea. RESULTS: In most (31/34) 'no pathology' patients, ORPN2 and ORPNR were unchanged (ΔORP -0.05 to 0.05; N = 15) or higher (0.1-0.63) in the second half. Changes in ORPN2 on CPAP were bidirectional and often large (5-95% confidence interval was -0.62 to 0.25). There was an excellent correlation between ΔOPRN2 and ΔORPNR in both groups (r > 0.90) emphasizing the importance of changes in N2-depth, when they occur, to changes in overall sleep depth. Changes in N1 time, N3 time and arousal/awakening index also correlated, but less strongly, with ΔORPNR (r = 0.76, -0.54, 0.69, respectively). CONCLUSIONS: N2 sleep depth can change dramatically in the same individual under different conditions. Ignoring these changes may result in inaccurate assessment of changes in overall non-REM sleep quality.
OBJECTIVES: Depth of sleep within non-rapid-eye-movement (non-REM) stage-2 (N2-depth) varies from being nearly similar to stage-1 to nearly similar to stage-3. Differences in N2-depth are not captured by conventional indices of sleep depth (N1-N3 times, arousal/awakening index) when comparing sleep depth under different conditions. Magnitude of changes in N2-depth in the same individual under different experimental conditions, and the importance of measuring these changes are unknown. METHODS: We measured sleep depth using the odds-ratio-product (ORP), a continuous index of sleep depth (0 = deep sleep, 2.5 = full wakefulness) (Younes et al. (2015) ORP of sleep EEG as a continuous measure of sleep state. Sleep 38(4):641-54.). ORP in stage 2 (ORPN2) and in all non-REM (ORPNR) were measured, along with conventional indices (1) in the first and second halves of the night in 34 patients with no pathology, and (2) before and on continuous positive airway pressure (CPAP) in 75 patients with obstructive apnea. RESULTS: In most (31/34) 'no pathology' patients, ORPN2 and ORPNR were unchanged (ΔORP -0.05 to 0.05; N = 15) or higher (0.1-0.63) in the second half. Changes in ORPN2 on CPAP were bidirectional and often large (5-95% confidence interval was -0.62 to 0.25). There was an excellent correlation between ΔOPRN2 and ΔORPNR in both groups (r > 0.90) emphasizing the importance of changes in N2-depth, when they occur, to changes in overall sleep depth. Changes in N1 time, N3 time and arousal/awakening index also correlated, but less strongly, with ΔORPNR (r = 0.76, -0.54, 0.69, respectively). CONCLUSIONS: N2 sleep depth can change dramatically in the same individual under different conditions. Ignoring these changes may result in inaccurate assessment of changes in overall non-REM sleep quality.
Authors: Magdy Younes; Samuel T Kuna; Allan I Pack; James K Walsh; Clete A Kushida; Bethany Staley; Grace W Pien Journal: J Clin Sleep Med Date: 2018-02-15 Impact factor: 4.062
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Authors: Magdy Younes; Bethany Gerardy; Allan I Pack; Samuel T Kuna; Cecilia Castro-Diehl; Susan Redline Journal: Sleep Date: 2022-06-13 Impact factor: 6.313