Circadian and ultradian rhythms depend on the level of consciousness in disorders of consciousness.

Introduction
Eye opening in patients with disorders of consciousness (DOC) marks the onset of a cyclic pattern with and without arousal. In minimally conscious state (MCS) arousal may be accompanied with awareness, unlike in unresponsive wakefulness syndrome (UWS). The presence of circadian and/or ultradian rhythmicity in patients with DOC has not been well established. To this end, we analyzed actigraphy data with a method well-suited to account for the variable rhythms within and across days observed in this population.
Methods
We collected actigraphy data from 73 subjects (19 controls, 35 MCS, 19 UWS) over 7 days and performed analyses using PyActigraphy. Singular Spectrum Analysis, a data-driven technique, was used to decompose the signal into circadian and ultradian rhythms. Next, we will evaluate these results statistically and correlate patients’ clinical diagnoses using the Coma Recovery Scale-Revised with the phase of detected circadian rhythms.
Results
Data cleaning resulted in exclusion of 1 control (5.3%), 10 MCS (28.6%) and 9 UWS (45%) subject(s). Our preliminary results show that the strength of circadian and ultradian rhythms in actigraphy data decreases with consciousness from healthy controls to MCS and almost disappearing in UWS (Figure 1).
Conclusion
Preservation of circadian/ultradian rhythms seems associated with the level of consciousness. Rhythms appear almost absent in UWS patients, which suggests limited behavioral evidence for a sleep/wake cycle although eye opening is observed. Overall, the use of actigraphy could contribute to clinical assessments in DOC, and although data quality might be suboptimal, acquisition can be repeated easily.