By Lucy Piper

Sleep-wake disturbances are a persistent problem in people who have sustained a traumatic brain injury (TBI) and one that is underestimated by patients, study data indicate.

"[O]ur data suggest that posttraumatic [sleep-wake disturbances] transform into a chronic state of disease in a majority of patients with TBI", say the researchers led by Lukas Imbach (University Hospital Zurich, Switzerland).

Yet the 31 participants with TBI of varying severity significantly underestimated levels of sleep need and excessive daytime sleepiness, making self-assessment an unreliable means of monitoring. This raises the question of whether all patients with TBI should be referred for sleep studies, the team comments.

Actigraphy assessment of the TBI patients showed that they still needed significantly more night-time sleep 18 months after injury than 42 healthy individuals, averaging 8.1 hours per 24 hours versus 7.1 hours, with no increase in daytime sleep.

The researchers explain in Neurology that this increased sleep need in the first 6 months after injury is likely to serve as a means of brain repair, but with no change occurring between 6 and 18 months, they suggest that TBI could also induce long-term damage to sleep-wake circuits in the brain.

This damage is likely to occur even in those with mild TBI, the team adds, finding that a significant association between TBI severity and sleep-wake disorders at 6 months was no longer evident 1 year on.

Objective measures of sleepiness revealed markedly diminished sleep latencies among TBI patients at 18 months, and significantly more patients in this group than among controls had chronic objective excessive daytime sleepiness, at 67% versus 19%.

By contrast, subjective measures of excessive daytime sleepiness revealed normal findings for the TBI patients, with no difference compared with controls but significant differences between objective and subjective measures for the patients.

Given that excessive daytime sleepiness is associated with public safety hazards such as car accidents, Imbach and colleagues propose that "if reasonable suspicion of posttraumatic [sleep-wake disturbances] occurs, patients with TBI should preferably be examined with objective sleep laboratory examinations rather than self-reported sleep measures".

And they believe that evidence from their study should be incorporated into future guidelines on the management of patients with TBI.

But in a related editorial, Brian Edlow (Massachusetts General Hospital, Boston, USA) and Gert Jan Lammers (Leiden University Medical Center, the Netherlands) say that while the findings provide a basis for reconsidering the clinical management of chronic sleep-wake disturbances after TBI, more mechanistic and epidemiological data are needed and the link between abnormal sleep latency and impaired daytime performance needs to be firmly established first.

"Nevertheless, Imbach et al. make a compelling case that posttraumatic sleep-wake disorders may represent a silent epidemic", they conclude.

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