According to the Centers for Disease Control and Prevention (CDC), more than 2 million people in the United States suffer a traumatic brain injury (TBI) every year. Most people with a TBI will also experience a sleep-wake disturbance (a real or perceived change in night-time sleep with resulting daytime impairment, SWD).
Over the past 10 years, a group of scientists in Switzerland has been focusing their research on SWD after TBI. In 2015, Dr. Imbach and his colleagues published their results of a study in which they examined the sleep of 60 patients 6 months after the patients had experienced a TBI. They found that the presence of bleeding in the brain at the time of injury was the greatest risk factor for developing a SWD. A new study followed those same patients for another 12 months (18 months total), and we report the results of that study here.
Who were the participants in the study and what did they do?
The 60 participants in this study were selected from among 140 adults who had experienced a first-ever TBI. They each underwent a computerized tomographic (CT) scan within 4 hours after the TBI and detailed assessment with standard clinical metrics (e.g., the Glasgow Coma Scale, which is a rough measure of the severity of the brain injury). The participants were matched with 42 people who did not have a TBI but who were of similar age, sex, and sleepiness (control group). Eleven people in the control group dropped out of the study, leaving 31 with complete data from all testing.
The average age of participants was 33 in the TBI group and 36 in the control group. Eleven participants in each group were men.
All participants wore an actigraph for two weeks on two separate occasions: for those with a TBI, six months after having the TBI and then again 18 months after the TBI. (An actigraph, which looks like an oversized watch, is typically worn on the nondominant wrist [that is, if you are right-handed, you would wear it on your left wrist]. It contains an accelerometer and records movements. Once the testing period is complete, the data are downloaded from the device and analyzed off line.)
Participants also reported their subjective perceptions of sleepiness and daytime fatigue by way of Epworth Sleepiness (ESS) and Fatigue Severity (FSS) Scales at these same intervals.
Who were the researchers and what did they do?
Dr. Lukas Imbach and his colleagues in Zurich and Bern, Switzerland, conducted a number of objective measures of sleep in all of the participants in both groups. In the TBI group, this testing took place six months after the TBI and, again, 18 months later.
They performed overnight sleep tests (polysomnography), commencing at 23:00 and terminating at 07:00, before then assessing for participants’ increased propensity to daytime sleepiness by way of daytime nap studies (i.e., the Multiple Sleep Latency Test or MSLT). They compared the findings from the actigraphs, polysomnograms, and MSLTs and the FSS and ESS scores between the two groups, and among the TBI patients at two different time points following their head injuries.
What were the results of the study?
When measured over 24 hours with actigraphy, night-time sleep, but not daytime sleep, was longer in the TBI group (8.1 hours) as compared with the control group (7.1 hours).
Delta power, sleep fragmentation, and distribution of sleep stages on the polysomnogram were normal in the TBI group. Sleep latencies on the MSLT were shorter in the TBI group (an average of 7 minutes) as compared with the control group (11 minutes). Based on the MSLTs (objective measure), excessive daytime sleepiness (EDS) was present in 67% of people with a TBI and 19% of control subjects. These levels of EDS remained fairly constant in the TBI group when comparing results at six and 18 months after the injury.
When comparing the objective and subjective measures of EDS (that is, MSLT vs ESS and FSS), the researchers identified a mismatch, “indicating persistent misperception of sleep-wake disturbance” in the group with TBI.
The presence of bleeding in the brain with the TBI and more severe TBI (lower Glasgow Coma Scale scores) predicted objective metrics of increased sleep quantities at night only during the major sleep period and EDS at 6 months after the TBI. Although findings at 18 months following the TBI emphasize the chronic nature of the negative impact of TBI upon SWD, the 6-month association between bleeding in the brain with the TBI and initial clinical severity of the injury was inexplicably no longer evident at 18 months following TBI.
What were the authors’ conclusions?
“We now provide long-term, prospective, controlled, and electrophysiologic evidence that sleepiness and [increased sleep need] remain a significant problem not only in the first months after TBI, but also in the long run.”
Imbach LL, Buechele F, Balko PO, Li T, Maric A, Stover JF, Bassetti CL, Mica L, Werth E, Baumann C. Sleep-wake disorders persist 18 months after traumatic brain injury but remain underrecognized. Neurology. 2016 ePub ahead of print.
An accompanying editorial to this paper concludes that, “Imbach et al. make a compelling case that posttraumatic sleep-wake disorders may represent a silent epidemic. With epidemiologic studies showing rising rates of TBI in civilian and military populations over the last decade, and with Imbach et al. now showing that the majority of patients with TBI have objective evidence of sleep-wake disturbance, the authors of future clinical guidelines will need to consider the emerging evidence supporting sleep studies in the care of patients with TBI.”
Edlow BL, Lammers GJ. Bringing posttraumatic sleep-wake disorders out of the dark. Neurology. 2016 ePub ahead of print.
It is important to realize that, although the MSLT results showed a shortened sleep latency in the participants with TBI, as compared with those without TBI, actigraphy identified no differences between the two groups with regard to amount of time spent sleeping during the daytime.
Note also that the overnight sleep studies were terminated at 0700, resulting in a maximum potential sleep time at night of 8 hours. Thus, while 67% of participants with TBI had a mean sleep latency of less than 8 minutes on the MSLT and would therefore meet International Classification of Sleep Disorders-3rd edition (ICSD-3) criteria for idiopathic hypersomnia, how many may have qualified for a diagnosis based on an overall sleep length exceeding 11 hours is not clear based on how the testing was conducted. It remains to be determined whether TBI, no matter how severe initially, might contribute to hypersomnia otherwise presumed to be “idiopathic,” and, if eventually deemed to meet ICSD-3 criteria for idiopathic hypersomnia, what the implications might be for prognosis and treatment.
This article was written by a volunteer medical writer and reviewed by David Rye, MD, PhD.