Consciousness recovery after a severe brain injury was suspected by researchers from the University of Surrey and the University of Salzburg, Austria, to depend on circadian rhythms. Circadian rhythms are an approximate 24-hour cycle governed by the body’s internal clock and they determine a number of physiological processes in the body including core body temperature, which fluctuates throughout the day. To assess the patients’ body temperatures, researchers used four external skin sensors to monitor each patient’s circadian rhythm. The level of consciousness of each patient was evaluated through the Coma Recovery Scale-Revised, which measured responsiveness to sound. The researchers found that those patients with a stronger arousal had body temperature patterns that were more closely aligned with a healthy 24-hour rhythm. In a separate investigation using bright light to measure arousal, a similar alignment with a healthy 24-hour circadian rhythm was found. The research reveals that circadian body temperature holds vital clues to the state of consciousness of patients. These clues have the potential to enable doctors to tailor brain injury medical treatment more effectively.