Year: 2020
Type: dissertation
Study design: Observational Study
Abstract: As survival rates from critical illness improve, strategies to return patients to their pre-morbid cognitive and functional status are important research priorities. Upwards of 9 out of 10 ICU survivors will suffer some degree of cognitive impairment at hospital discharge and approximately half will have decrements that persist for years. While the mechanisms for this newly acquired brain injury are poorly understood, several risk factors have been identified. Unfortunately, it is unclear how to accurately predict long-term cognitive impairment. We undertook a multisite, prospective, longitudinal cohort study of sleep, electroencephalography and cognitive outcome in survivors of critical illness. Our hypotheses being that sleep and circadian disruption would negatively impact long-term cognitive impairment in survivors of critical illness, a relationship that may be modified by Apolipoprotein E genotype. Further, cortical electrophysiological activity may predict, and therefore serve as an intermediate endpoint, long-term cognitive outcomes. In our cohort, the quantity and quality of sleep remained poor on the ward after ICU but was not terribly dissimilar to that experienced by patients hospitalized for noncritical illness by literature review. A number of risk factors for poor sleep including admission diagnosis (sepsis, post-operative admission, higher severity of illness). The other key finding of our cohort study was that rest-activity fragmentation was associated with worse cognitive impairment shortly after ICU discharge. This relationship, however, was lost at 6- and 12-months follow-up. Sleep and circadian variables studied did not seem to predict cognitive impairment at 6- or 12-months after ICU discharge. As the first multisite study to comprehensively examine the relationship between sleep, circadian function, and long-term cognitive impairment in survivors of critical illness, the single greatest limitation of this study is its internal validity as we experienced high losses to follow-up and unanticipated deaths. A larger study with more frequent covariate sampling might better elucidate the trajectory of recovery between sleep, circadian rhythm and long-term cognition. Promising preliminary analyses of electroencephalography data would suggest that early poor cognitive performance after ICU discharge correlates with changes primarily seen in subcortical white matter. Further analyses of this data are ongoing.
Source: TSpace (University of Toronto)
Author: Elizabeth Wilcox
Language: English
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W3156169242