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

Background and aims: 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 seven 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 one control
(5.3%), 10 MCS (28.6%) and nine 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.