Conflicted clocks: social jetlag, entrainment and the role of chronotype: From physiology to academic performance; from students to working adults

Giulia Zerbini

Research output: ThesisThesis fully internal (DIV)

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Sleep is essential for health and performance and its timing and consolidation are regulated by the biological clock. There is a rich variety in sleep timing (chronotype) that is often disregarded by society when imposing uniform school/working starting times. This leads to a phenomenon called social jetlag, the mismatch between biological and social clocks.

The main objectives of this thesis were to describe the consequences that arise from social jetlag, to explore possible solutions to reduce it, and to better understand entrainment (the process that keeps the biological clock synchronized with the external light-dark cycle).

We found that the impact of chronotype on school grades (late chronotypes usually obtain lower grades) was stronger in the early morning and for scientific subjects. Late chronotypes were more often absent from class, which, in turn, was associated with lower grades. We tested simple protocols to decrease social jetlag involving room light and blue light blocking glasses. Although social jetlag was not reduced, our findings show that simple ‘in-home’ light interventions are potentially effective in modifying the phase of entrainment and sleep timing. Finally, we have shown that season can influence school attendance and school performance, and that the weekly structure (workdays vs work-free days) has an impact on the sleep-wake cycle and on the melatonin rhythm, especially in late chronotypes.

The findings of this thesis have potential applications for society. Suggestions to improve school policies and practical solutions to delayed sleep phase derive from this work.
Translated title of the contributionKlokken in conflict: social jetlag, entraineren en de rol van het chronotype
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • University of Groningen
  • Merrow, Martha, Supervisor
  • Beersma, Domien, Supervisor
  • Kantermann, Thomas, Co-supervisor
Award date18-Sep-2017
Place of Publication[Groningen]
Print ISBNs978-94-034-0036-5
Electronic ISBNs978-94-034-0035-8
Publication statusPublished - 2017

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