The Association Between Sleep and Cognitive Function in People With Spinal Cord Injury (SCI)

Purpose/Objective: While there is evidence in other clinical groups to suggest that sleep problems can negatively impact cognitive performance, this relationship has not yet been examined in people with spinal cord injury (SCI). Thus, we sought to examine the association between sleep and cognitive function in people with SCI. Research Method/Design: Over the course of 7 days, 167 individuals with SCI completed daily subjective ratings of sleep (sleep quality, number of hours slept per night, and bedtime variability) and wore a wrist-worn device that continuously monitored autonomic nervous system (ANS) activity (i.e., blood volume pulse [BVP] signal and electrodermal activity [EDA] signal). At the end of this home monitoring period, participants completed a subjective rating of cognition and six objective cognitive tests. A series of multivariable linear regressions were used to examine associations between eight measures of sleep/ANS activity during sleep and eight cognitive variables. Results: Subjective ratings of sleep were not related to either objective cognitive performance or self-reported cognitive function. However, there were some relationships between ANS activity during sleep and objective cognitive performance: lower BVP signal was associated with poorer performance on measures of processing speed, working memory, learning and long-term memory, and EDA signals were associated with poorer performance on a measure of executive function. Conclusions/Implications: Future work is needed to better understand the relationship of sleep, especially sleep physiology, and cognitive functioning for individuals with SCI, and how that may be similar or different to relationships in the general population. Impact and Implications Sleep problems may be associated with cognitive problems in people with spinal cord injury (SCI). Given that objective measures of sleep were more predictive of cognitive outcomes than self-reported measures of sleep, clinicians may need to assess sleep by objective means (e.g., polysomnography, sleep diary plus actigraphy) to elucidate relationships between sleep and cognition. Future work is needed to determine if improvements in sleep may result in better cognitive functioning in people with SCI.