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We aimed to develop a data\u2010driven continuous measure of sleep depth\u2014ordinal sleep depth (OSD)\u2014using a deep learning framework, and to evaluate its correlation with arousal probability and its association with age, sex, sleep\u2010disordered breathing (SDB) and cognitive impairment. We used 21,787 polysomnography recordings from 18,116 unique patients. A convolutional neural network was trained on 3\u2010s EEG segments to estimate sleep depth continuously, incorporating ordinal regression for the ordered nature of non\u2010REM stages. OSD was compared with the odds ratio product (ORP). Correlations with sleep stages, Arousal Index and clinical variables were assessed. OSD showed a strong linear correlation with arousal probability (Pearson's\n                    <jats:italic>r<\/jats:italic>\n                    \u2009=\u20090.994), slightly outperforming ORP (\n                    <jats:italic>r<\/jats:italic>\n                    \u2009=\u20090.923). Both OSD and ORP reflected expected decreases in sleep depth with advancing age and demonstrated that females have significantly deeper sleep than males across several stages. OSD more accurately captured sleep depth reductions associated with SDB and increasing levels of cognitive impairment, showing significant reductions across all non\u2010REM stages in patients with an increased level of cognitive impairment. OSD as a data\u2010driven measure of sleep depth correlates strongly with arousal probability and effectively captures variations associated with age, sex, SDB and cognitive impairment. The results validate depth as an important dimension of sleep. OSD and ORP provide a nuanced understanding of sleep architecture with physiological and pathological implications.\n                  <\/jats:p>","DOI":"10.1111\/jsr.70074","type":"journal-article","created":{"date-parts":[[2025,4,25]],"date-time":"2025-04-25T06:10:13Z","timestamp":1745561413000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Ordinal Sleep Depth: A Data\u2010Driven Continuous Measurement of Sleep Depth"],"prefix":"10.1111","volume":"35","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-1580-4170","authenticated-orcid":false,"given":"Erik\u2010Jan","family":"Meulenbrugge","sequence":"first","affiliation":[{"name":"Department of Neurology Beth Israel Deaconess Medical Center  Boston Massachusetts USA"},{"name":"Division of Sleep Medicine Harvard Medical School  Boston Massachusetts USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Haoqi","family":"Sun","sequence":"additional","affiliation":[{"name":"Department of Neurology Beth Israel Deaconess Medical Center  Boston Massachusetts USA"},{"name":"Division of Sleep Medicine Harvard Medical School  Boston Massachusetts USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6029-2450","authenticated-orcid":false,"given":"Wolfgang","family":"Ganglberger","sequence":"additional","affiliation":[{"name":"Department of Neurology Beth Israel Deaconess Medical Center  Boston Massachusetts USA"},{"name":"Division of Sleep Medicine Harvard Medical School  Boston Massachusetts USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Samaneh","family":"Nasiri","sequence":"additional","affiliation":[{"name":"Department of Neurology Massachusetts General Hospital  Boston Massachusetts USA"},{"name":"Department of Biomedical Informatics Emory University School of Medicine  Atlanta Georgia USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5575-3953","authenticated-orcid":false,"given":"Robert J.","family":"Thomas","sequence":"additional","affiliation":[{"name":"Division of Sleep Medicine Harvard Medical School  Boston Massachusetts USA"},{"name":"Division of Pulmonary, Critical Care and Sleep, Department of Medicine Beth Israel Deaconess Medical Center  Boston Massachusetts USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"M. Brandon","family":"Westover","sequence":"additional","affiliation":[{"name":"Department of Neurology Beth Israel Deaconess Medical Center  Boston Massachusetts USA"},{"name":"Division of Sleep Medicine Harvard Medical School  Boston Massachusetts USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2025,4,25]]},"reference":[{"key":"e_1_2_8_2_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.neubiorev.2023.105465"},{"key":"e_1_2_8_3_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.compbiomed.2007.03.001"},{"key":"e_1_2_8_4_1","doi-asserted-by":"publisher","DOI":"10.1093\/jamia\/ocy131"},{"key":"e_1_2_8_5_1","doi-asserted-by":"publisher","DOI":"10.1111\/j.1365\u20102869.2008.00713.x"},{"key":"e_1_2_8_6_1","doi-asserted-by":"publisher","DOI":"10.1183\/16000617.0166\u20102023"},{"key":"e_1_2_8_7_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.yfrne.2017.07.004"},{"key":"e_1_2_8_8_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.jneumeth.2012.04.018"},{"key":"e_1_2_8_9_1","doi-asserted-by":"publisher","DOI":"10.1080\/07420520500263235"},{"key":"e_1_2_8_10_1","doi-asserted-by":"publisher","DOI":"10.1038\/s41591\u2010018\u20100268\u20103"},{"key":"e_1_2_8_11_1","volume-title":"The AASM Manual for the Scoring of Sleep and Associated Events: Rules, Terminology and Technical Specifications","author":"Iber C.","year":"2007"},{"key":"e_1_2_8_12_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.ijpsycho.2016.09.001"},{"key":"e_1_2_8_13_1","doi-asserted-by":"publisher","DOI":"10.1093\/sleep\/zsae180"},{"key":"e_1_2_8_14_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.jsmc.2017.09.001"},{"key":"e_1_2_8_15_1","volume-title":"Epidemiology of Sleep: Age, Gender, and Ethnicity","author":"Lichstein K. 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