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Certain sleep positions or excessive position changes can be related to some diseases and poor sleep quality. Nevertheless, sleep position is usually classified into four discrete values: supine, prone, left and right. An increase in sleep position resolution is necessary to better assess sleep position dynamics and to interpret more accurately intermediate sleep positions. This research aims to study the feasibility of smartphones as sleep position monitors by (1) developing algorithms to retrieve the sleep position angle from smartphone accelerometry; (2) monitoring the sleep position angle in patients with obstructive sleep apnea (OSA); (3) comparing the discretized sleep angle versus the four classic sleep positions obtained by the video-validated polysomnography (PSG); and (4) analyzing the presence of positional OSA (pOSA) related to its sleep angle of occurrence. Results from 19 OSA patients reveal that a higher resolution sleep position would help to better diagnose and treat patients with position-dependent diseases such as pOSA. They also show that smartphones are promising mHealth tools for enhanced position monitoring at hospitals and home, as they can provide sleep position with higher resolution than the gold-standard video-validated PSG.<\/jats:p>","DOI":"10.3390\/s21113689","type":"journal-article","created":{"date-parts":[[2021,5,26]],"date-time":"2021-05-26T21:56:44Z","timestamp":1622066204000},"page":"3689","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":16,"title":["Enhanced Monitoring of Sleep Position in Sleep Apnea Patients: Smartphone Triaxial Accelerometry Compared with Video-Validated Position from Polysomnography"],"prefix":"10.3390","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-0281-9023","authenticated-orcid":false,"given":"Ignasi","family":"Ferrer-Lluis","sequence":"first","affiliation":[{"name":"Institute for Bioengineering of Catalonia (IBEC), Barcelona Institute of Science and Technology (BIST), 08028 Barcelona, Spain"},{"name":"Centro de Investigaci\u00f3n Biom\u00e9dica en Red de Bioingenier\u00eda, Biomateriales y Nanomedicina (CIBERBBN), 28029 Madrid, Spain"},{"name":"Department of Automatic Control (ESAII), Universitat Polit\u00e8cnica de Catalunya-Barcelona Tech (UPC), 08028 Barcelona, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7493-1268","authenticated-orcid":false,"given":"Yolanda","family":"Castillo-Escario","sequence":"additional","affiliation":[{"name":"Institute for Bioengineering of Catalonia (IBEC), Barcelona Institute of Science and Technology (BIST), 08028 Barcelona, Spain"},{"name":"Centro de Investigaci\u00f3n Biom\u00e9dica en Red de Bioingenier\u00eda, Biomateriales y Nanomedicina (CIBERBBN), 28029 Madrid, Spain"},{"name":"Department of Automatic Control (ESAII), Universitat Polit\u00e8cnica de Catalunya-Barcelona Tech (UPC), 08028 Barcelona, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Josep Maria","family":"Montserrat","sequence":"additional","affiliation":[{"name":"Sleep Lab, Pneumology Service, Hospital Cl\u00ednic de Barcelona, 08036 Barcelona, Spain"},{"name":"Centro de Investigaci\u00f3n Biom\u00e9dica en Red de Enfermedades Respiratorias (CIBERES), 28029 Madrid, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6541-8729","authenticated-orcid":false,"given":"Raimon","family":"Jan\u00e9","sequence":"additional","affiliation":[{"name":"Institute for Bioengineering of Catalonia (IBEC), Barcelona Institute of Science and Technology (BIST), 08028 Barcelona, Spain"},{"name":"Centro de Investigaci\u00f3n Biom\u00e9dica en Red de Bioingenier\u00eda, Biomateriales y Nanomedicina (CIBERBBN), 28029 Madrid, Spain"},{"name":"Department of Automatic Control (ESAII), Universitat Polit\u00e8cnica de Catalunya-Barcelona Tech (UPC), 08028 Barcelona, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,5,26]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"264","DOI":"10.1016\/j.sleep.2019.07.016","article-title":"Sleep, suicide behaviors, and the protective role of sleep medicine","volume":"66","author":"Bishop","year":"2019","journal-title":"Sleep Med."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"373","DOI":"10.1111\/eip.12898","article-title":"Sleep disturbances in youth at-risk for serious mental illness","volume":"14","author":"Stowkowy","year":"2019","journal-title":"Early Interv. 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