Second international School On Mind, Brain And Education

2007, May 22-26

Basic and Applied Topics
in Biological Rhythms and Learning

Directors: Antonio M. Battro and Kurt W. Fischer
Program officer: María Lourdes Majdalani

Abstract: M. Angeles Rol de Lama

Teaching biological rhythms in endocrinology: cortisol, wrist temperature and impact of weekend night’s fever
This work has been developed as part of the Chronobiology student’s laboratory formation from Biology degrees at the University of Murcia. It is our intention to get the students of Endocrinology and Metabolism acquainted with the importance of diurnal fluctuations for diagnostic purposes. At the same time they get involved in research using their theoretical background. Endocrinology and Metabolism is a one-term course that is taught in the fourth year.
In humans cortisol circadian rhythm peaks in the morning and shows lowest levels during the midnight. This fluctuation of cortisol plasma level is reflected in saliva, allowing a simple, non invasive and unstressful sample collection. Most of our students are submitted to common phase shifts in their sleep pattern during the weekend, the present experiment was focussed to evaluate whether cortisol secretion on Mondays was affected by these “wakefully” weekends. A total of 10 volunteer students (5 women and 5 men) took part in the study. They collected saliva samples immediately after awakening and 4, 8, and 14 hours later on a representative weekday and on a Monday. In addition they volunteers completed a sleep/wake cycle and meal time diary for two weeks and their peripheral temperature (iButtom®, Thermochron) was monitored for the same period.
Our preliminary results shows that although Friday or Saturday night the sleep period was phase delayed neither cortisol profile nor temperature profile on Monday were affected. It could be argued that one day rest (Sunday) was enough to resynchronise cortisol rhythm, or that just one night of going out to have fun did not affect these circadian system marker rhythms or even that young people circadian system adapts rapidly to this phase shifts.