A new study published in the journal Neurology sheds light on the complex biological process of sleep in patients with traumatic brain injury (TBI).

It is well known in the medical community that victims of moderate to severe TBI have sleep–wake cycles that are seriously disrupted, with overlapping periods of sleep and wakefulness lasting several minutes. The team of Nadia Gosselin, a professor in Université de Montréal's Department of Psychology, has demonstrated that recovery of the sleep–wake cycle is closely linked to the degree of recovery of consciousness. Normal sleep–cycle is defined as a wake state during the day and sleep during the night.

“The study contributes to better understanding of why patients with acute traumatic brain injury have significant sleep and wakefulness problems," said Gosselin, who is also a researcher at the Centre for Advanced Research in Sleep Medicine at Hôpital du Sacré–Coeur de Montréal (CIUSSS du Nord–de–l’Île–de–Montréal). "Indeed, while sleep and wakefulness problems were thought to be mainly caused by the hospital environment and medications, the study shows that neurological impairment and alterations in levels of consciousness are factors that best explain these problems in the sleep–wake cycle."

However, added doctoral student Catherine Duclos, who is first author of the study published Dec. 21, "it is not yet possible to establish the type of relationship between consolidation of the normal sleep–wake cycle and consolidation of consciousness in patients: does one influence the other or is it a causal relationship? For the moment, we do not know. More research will have to be done to determine this."

To understand the dynamics of normal sleep recovery in TBI victims, Gosselin’s team followed the 24–hour sleep–wake cycle of 30 patients (22 men and 8 women, ages 17 to 58, in the acute phase of moderate or severe TBI. The study subjects were selected from ICU patients at Hôpital Sacré–Coeur de Montréal who had emerged from a coma. Several variables were controlled for in selecting the subjects. For example, patients who had pre–existing neurological problems or sleep disorders were excluded.

The researchers followed the patients during their stay in the neurological unit. The patients were victims of road accidents, falls or sports accidents. The research team observed that their sleep was fragmented and scattered throughout the day and night. The study’s findings indicate that when the brain has not recovered sufficiently from severe TBI, it is unable to generate a normal 24–hour sleep–wake cycle. Moreover, these observations indicate that the sleep quality of these patients was not sufficient to ensure proper brain recovery.

"We know that the quality of sleep of hospitalized patients is not the best," said Gosselin. "But sleep is important for recovery, especially in TBI cases. Indeed, sleep is necessary for the generation of new neurons and brain plasticity, i.e., the formation of new connections between neurons. There may be a common underlying mechanism for TBI recovery and sleep recovery, and that's what we need to discover. We would also like to study how light and ambient noise in hospitals affect the sleep quality of TBI patients in order to establish care protocols that take these variables into account for optimal recovery."