Abstract

Vartanian, D. (2023). Ecology of sleep and circadian phenotypes of the Brazilian population [Master’s Thesis, University of São Paulo].

The text below is related to the project of this thesis. The final abstract can only be produced when the research is completed.

Theories related to sleep and circadian rhythms are already well-established in science. However, it is necessary to verify and test these same theories in more extensive samples to obtain a more accurate picture of the ecology of sleep and temporal phenotypes. This thesis undertakes this commitment, with the aim of mapping the expression of sleep-wake cycles and circadian phenotypes in the Brazilian adult population and investigating the hypothesis that latitude is associated with circadian rhythm regulation. The latitude hypothesis is based on the idea that regions located at latitudes near the poles have, on average, a lower annual incidence of sunlight compared to regions near the equator (latitude 0°). Therefore, it is deduced that regions near the equator have a stronger solar zeitgeber, which, according to chronobiology theories, could lead to a greater propensity for the synchronization of circadian rhythms in these populations, reducing the amplitude and diversity of circadian phenotypes. This would also give these populations a morning characteristic when compared to populations living far from the equator. To achieve the aforementioned objectives, this thesis project will rely on a data sample of sleep-wake cycle expression in the Brazilian population, composed of \(120,265\) subjects covering all Brazilian states. This data was obtained in 2017 and is based on the Munich ChronoType Questionnaire (MCTQ), a widely validated questionnaire used to measure circadian phenotypes based on the sleep-wake cycle expression of individuals in their last four weeks. The results will contribute to the validation of chronobiology theories and will generate greater knowledge about the regulation of circadian rhythms and sleep-wake cycles in the Brazilian population.

Keywords: Chronobiology. Biological rhythms. Chronotype. Circadian phenotype. Sleep. Complex systems. Entrainment. Latitude. Ecology. MCTQ.