Night owls of Rio de la Plata region: Real-life scenarios to understand the biological clock

The Río de la Plata region, comprising Argentina and Uruguay, exhibits a remarkably late chronotype across all age groups, from childhood to adulthood, setting it apart from other populations worldwide. This pervasive eveningness, is accompanied by significant sleep deficits and severe misalignment between internal time and societal demands, particularly in adolescents and young adults. The widespread implementation of school shifts in this region offers a unique ecological condition to assess the impacts of these chronobiological challenges. Morning shift students face severe sleep deprivation and heighten social jet lag, whereas afternoon and evening shift students show healthier sleep patterns. Furthermore, longitudinal studies in Uruguayan dancers provide compelling evidence for the plasticity of the circadian system, as chronotypes dynamically adapt to changes in social and environmental conditions. The Rio de la Plata region, which stands out for the nocturnality of its people and for the extensive use of educational shifts, provides a unique opportunity to explore the impact of late chronotypes within ecological contexts, in which it is possible and to disentangle its specific influence from other confounding factors such as social pressure. Understanding the implications of late chronotypes on the plasticity of the circadian system has become essential for informing future public policies. Such policies must be grounded in region-specific evidence to address the unique challenges faced by nocturnal populations in early-oriented societies, aiming to promote equitable opportunities for improving sleep, cognitive performance, well-being, and overall health.