Abstract
Objective: To investigate the relationship between the presence of a circadian body temperature rhythm and behaviourally assessed consciousness levels in patients with disorders of consciousness (DOC, i.e. vegetative state/unresponsive wakefulness syndrome [VS/UWS] or minimally conscious state [MCS]). Methods: In a cross-sectional study, we investigated the presence of circadian temperature rhythms across six to seven days using external skin temperature sensors in 18 patients suffering from DOC. Beyond this; we examined the relationship between behaviourally assessed consciousness levels and circadian rhythmicity. Results: Interestingly, analyses with Lomb-Scargle periodograms revealed significant circadian rhythmicity in all patients (range 23.5-26.3h). We found that especially scores on the arousal subscale of the Coma Recovery Scale-Revised (CRS-R) were closely linked to the integrity of circadian variations in body temperature. Finally, we piloted whether bright light stimulation could boost circadian rhythmicity and found positive evidence in two out of eight patients. Conclusion: In conclusion, the study provides first evidence for an association between circadian body temperature rhythms and arousal as a necessary precondition for consciousness. Thereby, our findings also make a case for circadian rhythms as a target for treatment as well as the application of diagnostic and therapeutic means at times when cognitive performance is expected to peak.