{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,18]],"date-time":"2026-08-18T05:05:25Z","timestamp":1787029525919,"version":"3.56.0"},"reference-count":82,"publisher":"MDPI AG","issue":"24","license":[{"start":{"date-parts":[[2020,12,15]],"date-time":"2020-12-15T00:00:00Z","timestamp":1607990400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Schweizerischer Nationalfonds zur F&amp;#x00F6;rderung der Wissenschaftlichen Forschung","award":["P0ZHP1-178697"],"award-info":[{"award-number":["P0ZHP1-178697"]}]},{"name":"Schweizerischer Nationalfonds zur F&amp;#x00F6;rderung der Wissenschaftlichen Forschung","award":["PCEFP1-181279"],"award-info":[{"award-number":["PCEFP1-181279"]}]},{"DOI":"10.13039\/501100012654","name":"Olga Mayenfisch Stiftung","doi-asserted-by":"publisher","award":["-"],"award-info":[{"award-number":["-"]}],"id":[{"id":"10.13039\/501100012654","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100012545","name":"Foundation for Research in Science and the Humanities","doi-asserted-by":"publisher","award":["STWF-17-008"],"award-info":[{"award-number":["STWF-17-008"]}],"id":[{"id":"10.13039\/100012545","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100006447","name":"Universit\u00e4t Z\u00fcrich","doi-asserted-by":"publisher","award":["Forschungskredit FK-18-047"],"award-info":[{"award-number":["Forschungskredit FK-18-047"]}],"id":[{"id":"10.13039\/501100006447","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100006447","name":"Universit\u00e4t Z\u00fcrich","doi-asserted-by":"publisher","award":["Clinical Research Priority Program \"Sleep and Health\""],"award-info":[{"award-number":["Clinical Research Priority Program \"Sleep and Health\""]}],"id":[{"id":"10.13039\/501100006447","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Sleep during infancy is important for the well-being of both infant and parent. Therefore, there is large interest in characterizing infant sleep with reliable tools, for example by combining actigraphy with 24-h-diaries. However, it is critical to select the right variables to characterize sleep. In a longitudinal investigation, we collected sleep data of 152 infants at ages 3, 6, and 12 months. Using principal component analysis, we identified five underlying sleep composites from 48 commonly-used sleep variables: Sleep Night, Sleep Day, Sleep Activity, Sleep Timing, and Sleep Variability. These composites accurately reflect known sleep dynamics throughout infancy as Sleep Day (representing naps), Sleep Activity (representing sleep efficiency and consolidation), and Sleep Variability (representing day-to-day stability) decrease across infancy, while Sleep Night (representing nighttime sleep) slightly increases, and Sleep Timing becomes earlier as one ages. We uncover interesting dynamics between the sleep composites and demonstrate that infant sleep is not only highly variable between infants but also dynamic within infants across time. Interestingly, Sleep Day is associated with behavioral development and therefore a potential marker for maturation. We recommend either the use of sleep composites or the core representative variables within each sleep composite for more reliable research.<\/jats:p>","DOI":"10.3390\/s20247188","type":"journal-article","created":{"date-parts":[[2020,12,15]],"date-time":"2020-12-15T09:12:57Z","timestamp":1608023577000},"page":"7188","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":33,"title":["Which Are the Central Aspects of Infant Sleep? The Dynamics of Sleep Composites across Infancy"],"prefix":"10.3390","volume":"20","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3962-5804","authenticated-orcid":false,"given":"Sarah F.","family":"Schoch","sequence":"first","affiliation":[{"name":"Department of Pulmonology, University Hospital Zurich, 8091 Zurich, Switzerland"},{"name":"Department of Psychology, University of Zurich, 8006 Zurich, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Reto","family":"Huber","sequence":"additional","affiliation":[{"name":"Child Development Center, University Children\u2019s Hospital Zurich, 8032 Zurich, Switzerland"},{"name":"Department of Child and Adolescent Psychiatry and Psychotherapy, Psychiatric Hospital, University of Zurich, 8008 Zurich, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Malcolm","family":"Kohler","sequence":"additional","affiliation":[{"name":"Department of Pulmonology, University Hospital Zurich, 8091 Zurich, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1432-4367","authenticated-orcid":false,"given":"Salome","family":"Kurth","sequence":"additional","affiliation":[{"name":"Department of Pulmonology, University Hospital Zurich, 8091 Zurich, Switzerland"},{"name":"Department of Psychology, University of Fribourg, 1700 Fribourg, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2020,12,15]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"302","DOI":"10.1542\/peds.111.2.302","article-title":"Sleep Duration from Infancy to Adolescence: Reference Values and Generational Trends","volume":"111","author":"Iglowstein","year":"2003","journal-title":"Pediatrics"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"13211","DOI":"10.1523\/JNEUROSCI.2532-10.2010","article-title":"Mapping of Cortical Activity in the First Two Decades of Life: A High-Density Sleep Electroencephalogram Study","volume":"30","author":"Kurth","year":"2010","journal-title":"J. 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