Premature birth and circadian preference in young adulthood: evidence from two birth cohorts

ABSTRACT

A preference for eveningness (being a “night owl”) and preterm birth (<37 weeks of gestation) are associated with similar adversities, such as elevated blood pressure, impaired glucose regulation, poorer physical fitness, and lower mood. Yet, it remains unclear if and how preterm birth is associated with circadian preference. The aim of this study was to assess this association across the whole gestation range, using both objective and subjective measurements of circadian preference.

Circadian preference was measured among 594 young adults (mean age 24.3 years, SD 1.3) from two cohorts: the ESTER study and the Arvo Ylppö Longitudinal Study. We compared 83 participants born early preterm (<34 weeks) and 165 late preterm (34 to <37 weeks) with those born at term (≥37 weeks, n = 346). We also compared very low birth weight (VLBW, <1500 g) participants with term-born controls. We obtained objective sleep data with actigraphs that were worn for a mean period of 6.8 (SD 1.4) nights. Our primary outcome was sleep midpoint during weekdays and weekend. The sleep midpoint is the half-way time between falling asleep and waking up, and it represents sleep timing. We also investigated subjective chronotype with the Morningness–Eveningness Questionnaire (MEQ) in 688 (n = 138/221/329) ESTER participants. The MEQ consists of 19 questions, which estimates the respondent to be of a “morning”, “evening,” or “intermediate” chronotype, based on the Morningness–Eveningness Score (MES). We analyzed the data from the actigraphs and the MES with three linear regression models, and analyzed distribution of the chronotype class with Pearson χ2.

There were no consistent differences across the study groups in sleep midpoint. As compared with those born at term, the mean differences in minutes:seconds and 95% confidence intervals for the sleep midpoint were: early preterm weekdays 11:47 (−8:34 to 32:08), early preterm weekend 4:14 (−19:45 to 28:13), late preterm weekdays −10:28 (−26:16 to 5:21), and late preterm weekend −1:29 (−20:36 to 17:37). There was no difference in sleep timing between VLBW-participants and controls either. The distribution of chronotype in the MEQ among all participants was 12.4% morningness, 65.4% intermediate, and 22.2% eveningness. The distribution of the subjective chronotype class did not differ between the three gestational age groups (p = 0.98). The linear regression models did not show any influence of gestational age group or VLBW status on the MES (all p > 0.5).

We found no consistent differences between adults born early or late preterm and those born at term in circadian preference. The earlier circadian preference previously observed in those born smallest is unlikely to extend across the whole range of preterm birth.

KEYWORDS:

• Preterm
• Actigraphy
• MEQ
• Chronotype

Supplemental data for this article can be accessed here.

Additional information

Funding

This study was supported by grants from the Academy of Finland (SALVE program for 2009–2012 and grants 127437, 129306, 130326, 134791, 263924, 274794 and 285547), Doctoral Programme in Clinical Research, University of Helsinki, Doctoral Programme in Psychology, Learning, and Communication, University of Helsinki, Doctoral programme for Public Health, University of Tampere, the Emil Aaltonen Foundation, European Commission (Framework 5 award QLG1-CT-2000-001643, H2020-PHC-2014, 633595 (DynaHEALTH) and EU H2020-SC1-2016-2017 (LifeCycle) to MRJ, H2020 award SC1-2016-RTD-733180 RECAP), the Foundation for Pediatric Research, the Finnish Government Special Subsidiary for Health Sciences (evo), Finnish Medical Societies: Duodecim and Finska Läkaresällskapet, the Jalmari and Rauha Ahokas Foundation, the Juho Vainio Foundation, the National Graduate School of Clinical Investigation, the Novo Nordisk Foundation, the Signe and Ane Gyllenberg Foundation, the Sigrid Jusélius Foundation, the Yrjö Jahnsson Foundation, the Bundesministerium für Forschung und Technik (Federal Government of Germany, Ministry of Science and Technology) program grants PKE 4 and JUG 14 (FKZ’s 0706224, 0706564, and 01EP9504), Samfundet Folkhälsan and Päivikki and Sakari Sohlberg Foundation.