New research published on Medscape suggests that circadian rhythms may indicate consciousness in patients with severe brain injuries. 

Researchers studied temperature rhythms for a week in all patients under a habitual light (HL) condition, which mimicked normal light conditions in the hospital environment. They collected temperature data using external skin sensors, two at proximal sites near the collarbone and two at distal sites near the ankles; they pooled data from each of the two sensors.

“We were specifically interested in the interdaily stability…of the rhythm, an index that informs about how well the patient’s temperature rhythms were entrained to a 24-hour zeitgeber (i.e., the light-dark cycle),”  the authors write.

In addition to interdaily stability, Dr Blume and her colleagues were interested in group differences in period length (the length of one cycle) and normalized power (indexing how pronounced the circadian rhythm was).