University of Oulu

Johan Björkqvist, Juho Kuula, Liisa Kuula, Markku Nurhonen, Petteri Hovi, Katri Räikkönen, Anu Pesonen & Eero Kajantie (2020) Chronotype in very low birth weight adults – a sibling study, Chronobiology International, 37:7, 1023-1033, DOI: 10.1080/07420528.2020.1754847

Chronotype in very low birth weight adults : a sibling study

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Author: Björkqvist, Johan1,2; Kuula, Juho2,3; Kuula, Liisa4;
Organizations: 1Children’s Hospital, and Pediatric Research Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
2Department of Public Health Promotion, Finnish Institute for Health and Welfare, Helsinki, Finland
3Department of Radiology, HUS Medical Imaging Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
4SleepWell Research Program, Faculty of Medicine, University of Helsinki, Finland
5Department of Psychology and Logopedics, Faculty of Medicine, University of Helsinki
6PEDEGO research unit, University of Oulu, Oulu, Finland
7Department of Clinical and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway
Format: article
Version: accepted version
Access: open
Online Access: PDF Full Text (PDF, 0.2 MB)
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Language: English
Published: Informa, 2020
Publish Date: 2021-08-24


Chronotype is the temporal preference for activity and sleep during the 24 h day and is linked to mental and physical health, quality of life, and mortality. Later chronotypes, so-called “night owls”, consistently display poorer health outcomes than “larks”. Previous studies have suggested that preterm birth (<37 weeks of gestation) is associated with an earlier chronotype in children, adolescents, and young adults, but studies beyond this age are absent. Our aim was to determine if adults born preterm at very low birth weight (VLBW, ≤1500 g) display different chronotypes than their siblings. We studied VLBW adults, aged 29.9 years (SD 2.8), matched with same-sex term-born siblings as controls. A total of 123 participants, consisting of 53 sibling pairs and 17 unmatched participants, provided actigraphy-derived data on the timing, duration, and quality of sleep from 1640 nights (mean 13.3 per participant, SD 2.7). Mixed effects models provided estimates and significance tests. Compared to their siblings, VLBW adults displayed 27 min earlier sleep midpoint during free days (95% CI: 3 to 51 min, p =.029). This was also reflected in the timing of falling asleep, waking up, and sleep-debt corrected sleep midpoint. The findings were emphasized in VLBW participants born small for gestational age. VLBW adults displayed an earlier chronotype than their siblings still at age 30, which suggests that the earlier chronotype is an enduring individual trait not explained by shared family factors. This preference could provide protection from risks associated with preterm birth.

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Series: Chronobiology international
ISSN: 0742-0528
ISSN-E: 1525-6073
ISSN-L: 0742-0528
Volume: 37
Issue: 7
Pages: 1023 - 1033
DOI: 10.1080/07420528.2020.1754847
Type of Publication: A1 Journal article – refereed
Field of Science: 3123 Gynaecology and paediatrics
Funding: Drs Björkqvist and Juho Kuula have received a salary from the Doctoral Programme in Clinical Research, University of Helsinki. Dr Liisa Kuula has received a research grant from the Academy of Finland. Academy of Finland [Grants 274794 and 315680 to Eero Kajantie, 1322035 and 12871741 to Anu Pesonen]; the European Commission [Horizon2020 award 733280 RECAP Research on Children and Adults Born Preterm]; the Finnish Foundation for Pediatric Research; Finska Läkaresällskapet; the Juho Vainio Foundation; the Novo Nordisk Foundation; the Signe and Ane Gyllenberg Foundation; the Sigrid Jusélius Foundation; and the Yrjö Jahnsson Foundation.
Copyright information: © 2020 Informa UK Limited, trading as Taylor & Francis Group. This is an Accepted Manuscript of an article published by Taylor & Francis in Chronobiology International on 30 Apr 2020, available online: