Background and aims Sleep is considered to play an important role in neuroplasticity and posttraumatic brain recovery. The assessment of sleep structure and sleep-wake cycle in subjects with disorders of consciousness (DOC) might be useful for predicting prognosis and treatment approach modification. In our study we assessed sleep structure and sleep-wake cycle by long-term (≥24h) polysomnography (PSG), melatonin and stress hormones levels in DOC patients - unresponsive wakefulness syndrome (UWS) and minimally conscious state (MCS).

Methods We included 27 patients (22–57 years old). Median time duration after the brain injury constituted 11 (1–96) months. We applied Coma Recovery Scale (CRS-R) for behavioral assessment and diagnosed UWS in 7 subjects and MCS in 20 patients (traumatic brain injury was the underlying reason in 20 subjects, hypoxia – in 5, other causes were verified in 2 cases). The full in-hospital attended PSG (Medicom, Russia) was recorded during 24 hours. Blood sampling for melatonin were evaluated 5 times a day (8.00, 15.00, 21.00, 00.00, 3.00), urine samples for melatonin were taken twice (day and night).

Results All (100%) patients demonstrated irregular sleep-wake cycle and fragmented, abnormal sleep structure, while 85% patients had normal melatonin level (within the reference values). Deep sleep was absent in 25% cases. REM sleep episodes, despite decreased duration, were present in the majority of patients (87%). There was no significant correlation between melatonin level and PSG parameters.

Conclusion In our study, DOC patients had irregular sleep-wake cycle and sleep structure violations. However, sleep-wake changes do not seem to be associated with the disorders of melatonin metabolism.

(the study is supported by the grant of the RFFR #19-29-01066)