Faculty Bibliography

Non-rapid eye movement (NREM) sleep has recently garnered support for its role in consolidating hippocampus-based declarative memories in humans. We provide a brief review of the latest research on NREM sleep activity and its association with declarative memory consolidation. Utilizing empirical findings from sleep studies on schizophrenia, Alzheimer's disease, and fibromyalgia, we argue that a significant reduction of slow-wave sleep and sleep spindle activity contribute to the development of deficits in declarative memory consolidation along with concomitant sleep disturbances commonly experienced in the aforementioned disorders. A tentative model is introduced to describe the mediating role of the thalamocortical network in disruptions of both declarative memory consolidation and NREM sleep. The hope is to stimulate new research in further investigating the intimate link between these two very important functions.

BACKGROUND: Individuals with traumatic brain injury (TBI) often develop sleep disorders post-injury. The most common one is insomnia, which can exacerbate other post-injury symptoms, including fatigue, impaired cognition, depression, anxiety, and pain. Cognitive Behavioral Therapy for Insomnia (CBT-I) is a manualized treatment that effectively treats insomnia with secondary effects on cognition, mood, and pain in various populations. OBJECTIVE: This paper reviews the use of CBT-I for three participants with TBI of different severities. METHODS: Pre- and post-treatment assessments of insomnia, fatigue, depression, anxiety, and pain were conducted. Mood was further assessed at follow-up. Minimal clinically important difference (MCID) scores derived from the research literature were used to establish clinically meaningful symptom improvement on self-report questionnaires. RESULTS: The reduction in insomnia severity scores for all three participants were not large enough to be considered a clinically significant improvement following CBT-I, although trends toward improvement were observed. However, all participants showed clinically significant reductions in anxiety at post-treatment; the effects persisted for 2 participants at follow-up. Reductions in depression symptoms were observed for 2 participants at post-treatment, and treatment effects persisted for 1 participant at follow-up. One participant endorsed clinically significant improvements in fatigue and pain severity. CONCLUSIONS: We conclude that CBT-I may provide secondary benefits for symptoms commonly experienced by individuals with TBI, especially mood disturbances.

PRIMARY OBJECTIVE: To characterize sleep architecture and self-reported sleep quality, fatigue and daytime sleepiness in individuals with TBI. Possible relationships between sleep architecture and self-reported sleep quality, fatigue and daytime sleepiness were examined. METHODS: Forty-four community-dwelling adults with TBI completed the Pittsburgh Sleep Quality Index (PSQI), Multidimensional Assessment of Fatigue (MAF) and Epworth Sleepiness Scale (ESS). They underwent two nights of in-laboratory nocturnal polysomnography (NPSG). Pearson product-moment correlation coefficients and hierarchical linear regression was used to analyse the data. RESULTS: Based on the PSQI cut-off score of >/= 10, 22 participants were characterized as poor sleepers. Twenty-seven participants met criteria for clinically significant fatigue as measured by the GFI of the MAF. Fourteen participants met criteria for excessive daytime sleepiness as measured by the ESS. Poor sleep quality was associated with poor sleep efficiency, short duration of stage 2 sleep and long duration of rapid eye movement sleep. There was little-to-no association between high levels of fatigue or daytime sleepiness with NPSG sleep parameters. CONCLUSIONS: A high proportion of the sample endorsed poor sleep quality, fatigue and daytime sleepiness. Those who reported poorer sleep quality evidenced a shorter proportion of time spent in stage 2 sleep. These findings suggest that disruptions in stage 2 sleep might underlie the symptoms of sleep disturbance experienced following TBI.

BACKGROUND: Obstructive sleep apnea (OSA) is commonly found in individuals with traumatic brain injury (TBI) and may exacerbate TBI-related symptoms. Nocturnal polysomnography (NPSG) is considered the gold standard for detecting the presence of sleep apnea. However, there is a limitation with its use known as the "first-night effect" (aberrant polysomnography findings on the first night in a sleep lab). OBJECTIVE: The primary objectives were to investigate the night-to-night consistency of diagnosing and classifying obstructive sleep apnea in individuals with TBI, and ascertain if individuals with TBI are prone to a first-night effect. METHODS: 47 community-dwelling adults with self-reported mild-to-severe TBI underwent two nights of in-laboratory NPSG to examine variability between the first and second night with regards to OSA diagnosis and severity as well as sleep architecture. RESULTS: OSA detection and severity were consistent from night-to-night in 89% of participants with TBI. Participants with TBI demonstrated longer REM latency on the first night compared to the second night of sleep study. CONCLUSIONS: These findings indicate that two nights of in-laboratory NPSG are generally consistent in reliably diagnosing OSA in individuals with TBI and that first-night effects are minimal. One night of NPSG has diagnostic utility in the evaluation of sleep disorders in individuals with TBI.