Circadian rhythm of temperature in head injury.

It has been shown in a previous study that head injured patients appear to have a circadian rhythm of their body functions. This needed to be confirmed using additional data, better collection methods and analysis. Additional goals were to develop a method of detrending of physiological time series in order to improve rhythm detection when it may be hidden behind a low frequency trend and the creation of a computer system for data acquisition and analysis. The temperature data of 10 head injured patients was studied using the Iterative Cosinor method. In one case, prior to the Cosinor method, detrending of the data was used using a specially designed polynomial fitting technique. The Iterative Cosinor method showed circadian rhythms in nine out of 10 patients. After detrending, a rhythm was found in the data of the 10th patient as well. The periods of the rhythm were around, but were not equal to, 24 hours. The results show that comatose head injured patients have a circadian rhythm of their core temperature. The detection of a circadian rhythm may, in some cases, be improved by using a detrending technique. The deviation of the rhythm period from 24 hours suggests that the rhythms found in these patients are free-running, meaning that head injured patients are not synchronized with their surroundings.