Chronotype in very low birth weight adults – a sibling study

ABSTRACT

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.

Abbreviations

AGA: Appropriate for gestational age; ELBW: Extremely low birth weight, ≤ 1000 grams; FMBR: Finnish Medical Birth Registry; HeSVA: Helsinki Study of Very low birth weight Adults; MSFsc: Midsleep on free days, corrected for sleep debt; SGA: Small for gestational age, ≤ −2 SD; VLBW: Very low birth weight, ≤ 1500 grams; WASO: Wake after sleep onset

KEYWORDS:

• Actigraphy
• sleep midpoint
• midsleep
• MSFsc
• VLBW
• very low birth weight
• preterm
• prematurity

Supplemental data

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Declaration of Interest

The authors report no conflicts of interest.

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Additional information

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. The other authors have indicated that they have no financial relationships relevant to this article to disclose.