Objective: Obstructive sleep apnea (OSA) has been associated with structural and functional brain changes and cognitive impairment in sleep clinic samples. Persons with traumatic brain injury (TBI) are at increased risk of OSA compared to community samples, and many experience chronic cognitive disability. However, the impact of OSA on cognitive outcome after TBI is unknown. The purpose of this study was to examine the relationship between polysomnographic sleep parameters on neuropsychological performance 2 years following TBI. We hypothesized that oxygen desaturation, sleep fragmentation, and sleep depth would predict neuropsychological performance. Method: Participants (N = 123) were persons with moderate-to-severe TBI who underwent Type 1 Polysomnography during acute neurorehabilitation. At 2 years post-TBI, participants completed telephone-based neuropsychological testing (the Brief Test of Adult Cognition by Telephone). General linear models were fit to investigate the relationship between sleep parameters and neuropsychological performance, controlling for demographics and posttraumatic amnesia. Results: When controlling for demographics, injury characteristics, and other sleep parameters, greater percent of Stage 1 sleep time predicted poorer cognitive performance (Overall BTACT composite, p = 0.0078, ηp2 = 6.6%; Verbal Memory composite, p = 0.0407, ηp2 = 3.9%; Executive Function composite, p = 0.0215, ηp2 = 4.9%). Oxygen desaturation, cortical arousals, Stage 3 sleep, and the obstructive apnea-hypopnea index were not significantly associated with cognitive outcome. Conclusions: Reduced sleep depth was associated with cognitive outcome in persons with TBI; these findings require replication. Future research should examine whether improving sleep (e.g. increasing deep sleep) during acute recovery can improve cognitive recovery following TBI.
Keywords: Brain Injuries, traumatic; cognition; cohort studies; polysomnography; sleep initiation and maintenance disorders.