Recovery of consciousness of patients with severe brain injuries is found to be linked to circadian body temperature variations in a new study by researchers at the University of Surrey and the University of Salzburg, Austria. Circadian rhythms determine a number of physiological processes in the body including core body temperature, which fluctuates throughout the day. The researchers examined circadian body temperature variations of 18 patients suffering from severe brain injuries. The level of consciousness of each patient was evaluated through the Coma Recovery Scale-Revised, which among others measures responsiveness to sound or a patient’s ability to spontaneously open eyes without or only with stimulation by the examiner. Researchers discovered that patients who scored better on the Coma Recovery Scale-Revised, especially, those patients with a stronger arousal had body temperature patterns that were more closely aligned with a healthy 24-hour rhythm. This finding suggests that patient’s consciousness levels should be assessed during time windows when their circadian rhythm predicts them to be more responsive. Researchers also examined the effects of bright light stimulation on patients with severe brain injuries. After one week, improvements were found in the level of consciousness of some patients. The study finds that the closer the body temperature patterns of a severely brain injured person are to those of a healthy person’s circadian rhythm, the better they scored on tests of recovery from coma, especially when looking at arousal, which is necessary for consciousness. Also, the study suggests that the time of the day when patients are tested could be important as well as providing an environment that replicates a normal light-dark cycle that supports a healthy circadian rhythm.