Late chronotype and associated health problems

Introduction: Chronotype reflects an individual's preference for activity and rest within a 24-hour period, governed by the internal circadian clock system located in the suprachiasmatic nuclei of the hypothalamus. There are three chronotypes: Morning, Evening, and Intermediate. The evening type is also called “night owls” or late chronotype. Night owls prefer to be active in the evening and sleep and wake up late. The misalignment between the sleep patterns in late chronotype and the social schedules puts the night owls in danger of physical and mental health issues. Purpose of work: The primary aim of this review is to provide a comprehensive overview of current knowledge on the impact of late chronotype on health. Methods and materials: A review of the literature available in the PubMed database, the following keywords and their combinations were searched: "chronotype", “mental health", "cancer", “late chronotype”, “circadian rhythm”, “type 2 diabetes”, “depression”. State of knowledge: Studies have confirmed that late chronotype is associated with a higher risk of type 2 diabetes, obesity, cancer, alcohol and cigarette addiction, and unhealthy eating habits. Furthermore, the evening chronotype is an independent risk factor for depression. It is also linked with anxiety, bipolar disorder, and schizophrenia. Summary: In this review, we have summarized the latest research on late chronotype, circadian misalignment, and their potential consequences on human health. Most studies on evening chronotype and related health issues are cross-sectional. Further longitudinal or experimental research is needed to examine the potential cause-and-effect relationships on this cause.