Association Between the Individual Chronotype and Body Composition in German Students - The ChroNu Study

Chronotype is defined as the midpoint of sleep and describes a biological construct of an organism's temporal organisation. Misalignment between the individual chronotype and socially determined schedules may result in a phenomenon called "social jetlag". Emerging evidence indicates that both, a later chronotype and/or a substantial "social jetlag" adversely affects metabolic health. Young adults may be particularly vulnerable to these exposures since the chronotype progressively delays from adolescence until early adulthood (approx. 20 years of age) before it advances again. Simultaneously, education in institutions or working hours starts early during the day, potentially contribute to substantial "social jetlag". Data on the development of overweight / obesity prevalence in Germany indicates that rates are now constant or declining in most adult age groups, with the clear exception of young adults, in whom rates continue to be on the rise. Nonetheless, the potential contribution of chronotype and/or social jetlag to this secular trend has not been addressed in Germany. Hence, the hypothesis of the ChroNu cohort is that individual chronotype and social jetlag are predictors of (changes in) the body composition in young adulthood (ages 18-25 years) and that changes in chronotype / social jetlag will result in changes in body composition. The ChroNu cohort forms part of the overall ChroNu study, which addresses the hypothesis that timing of food intake which diverges from the individual chronotype constitutes a characteristic of social jetlag which has adverse short- and long-term consequences for metabolic health (see The ChroNustudy). This study will recruit 300 healthy, non-obese students aged 18-25 years enrolled at Paderborn University until February 2020 and follow these up one year later. Chronotype and social jetlag will be determined using the validated MCTQ. Body composition will be assessed by bioimpedance analysis (BIA) The ChroNu cohort study will revea