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: José Antonio Sarabia

A new simple and non invasive tool to analyse circadian rhythmicity in normal free living subjects
The importance of circadian system in human being has long been proved, since most of behavioural, psychological and biological variables exhibit circadian rhythms. In addition, it is more and more evident that to diagnose and treat several human disorders the information obtained from a single time point is only partial and long period recording becomes necessary. This study is focussed to validate two different non invasive and wireless data loggers, one for peripheral wrist temperature (WT) and other for environmental temperature and light exposure. Thus, we can obtain, simultaneously at the same subject, recordings from a marker rhythm (WT) and two of the more important zeitgebers: light and temperature.
The ThermoChron® from I-button (IDC S:A., Spain) is a temperature sensor that allows automatic recordings every 10 minutes for 14 days. It is attached to the inner side of a sport wristband, and located on the radial artery. We have been using this device for more than two years and with more than 150 students who volunteered to participate. More recently, environmental light and temperature have been also monitored using a Hobbo® sensor, in 30 students.
Our data demonstrate that WT wireless recording can be considered a reliable marker rhythm to evaluate circadian system status. The use of wireless data logger allow us to record long term data series in free living individuals, minimizing disturbances to the experimental subjects. In addition, complementary environmental light provides additional information to determine whether possible alterations in the circadian system can be attributed to exposure to light pollution during the night or lack of brilliant light during the day, that is, conflicting inputs to the circadian clock. Environmental temperature recordings are also important, taking into account that skin temperature can change in accordance to thermoregulation needs.
In conclusion, ThermoChron® together with Hobbo® sensor recordings allow to obtain reliable information at the same time from both circadian system output and input in free living subjects.